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Introduction to Conditions

 

Boolean Variables

 

Introduction

When interacting with a computer, a user submits values to a running application. Some of these values are valid. Some other values must be rejected or changed. To take care of these, the values must be checked, examined, re-examined, etc. The validity of a value is checked against its type. For example, a number can be checked as being equal to another. A condition can be checked as being true. A measure can be checked as to whether it is higher than a certain threshold.

To perform the necessary validations of values, the C++ language provides some symbols, referred to as Boolean operators.

Practical LearningPractical Learning: Introducing Conditions

  1. Start Microsoft Visual C++ 2005
  2. On the main menu, click File -> New -> Project...
  3. On the left side, make sure that Visual C++ is selected. In the Templates list, click CLR Empty Project
  4. In the Name box, replace the string with FlowerShop2 and click OK
  5. On the main menu, click Project -> Add Class...
  6. In the Categories lists, expand Visual C++ and click C++.
    In the Templates list, make sure C++ Class is selected and click Add
  7. Set the Name of the class to CFlower and click Finish
  8. Complete the Flower.h header file as follows:
     
    #pragma once
    using namespace System;
    
    public ref class CFlower
    {
    private:
        int _tp;
        int _clr;
        __wchar_t _arg;
        double   _price;
    
    public:
        property int Type
        {
    	int get() { return _tp; }
    	void set(int tp) { _tp = tp; }
        }
    
        property int Color
        {
    	int get() { return _clr; }
    	void set(int clr) { _clr = clr; }
        }
    
        property __wchar_t Arrangement
        {
    	__wchar_t get() { return _arg; }
    	void set(__wchar_t arg) { _arg = arg; }
        }
    
        property double UnitPrice
        {
    	double get() { return _price; }
    	void set(double price) { _price = price; }
        }
    
    public:
        CFlower(void);
        CFlower(int type);
        CFlower(int type, int color,
                __wchar_t argn, double price);
        ~CFlower();
    };
  9. Complete the Flower.cpp source file as follows:
     
    #include "Flower.h"
    
    CFlower::CFlower(void)
        : _tp(0), _clr(0),
          _arg(L'B'), _price(45.95)
    {
    }
    
    CFlower::CFlower(int type)
        : _tp(type),
          _clr(0),
          _arg(L'B'),
          _price(35.95)
    {
    }
    
    CFlower::CFlower(int type, int color,
    	         __wchar_t argn, double price)
    {
        _tp = type;
        _clr = color;
        _arg = argn;
        _price = price;
    }
    
    CFlower::~CFlower()
    {
    }
  10. On the main menu, click Project -> Add Class...
  11. In the Templates list, make sure C++ Class is selected and click Add
  12. Set the Name of the class to COrderProcessing and click Finish
  13. Complete the OrderProcessing.h header file as follows:
     
    #pragma once
    #include "Flower.h"
    
    ref class COrderProcessing
    {
    private:
        int       _qty;
        CFlower ^ _flr;
    
    public:
        COrderProcessing(void);
        ~COrderProcessing();
    
        property CFlower ^ Flower
        {
    	CFlower ^ get() { return _flr; }
    	void set(CFlower ^ flr) { _flr = flr; }
        }
    
        property int Quantity
        {
    	int get() { return _qty; }
    	void set(int q) { _qty = q; }
        }
    
        double GetTotalPrice();
    };
  14. Complete the OrderProcessing.cpp source file as follows:
     
    #include "OrderProcessing.h"
    
    COrderProcessing::COrderProcessing(void)
    {
        _flr = gcnew CFlower;
    }
    
    COrderProcessing::~COrderProcessing()
    {
        delete _flr;
    }
    
    double COrderProcessing::GetTotalPrice()
    {
        return Quantity * _flr->UnitPrice;
    }
  15. To create one more source file, on the main menu, click Project -> Add New Item...
  16. In the Templates list, make sure C++ File (.cpp) is selected.
    Set the Name to Exercise and click Add
  17. Complete the file as follows:
     
    #include "Flower.h"
    #include "OrderProcessing.h"
    using namespace System;
    
    COrderProcessing ^ CreateFlowerOrder()
    {
        COrderProcessing ^ order = gcnew COrderProcessing;
        int type, color, qty;
        __wchar_t arrangement;
        double price;
    
        Console::WriteLine(L"=======================");
        Console::WriteLine(L"==-=-=Flower Shop=-=-==");
        Console::WriteLine(L"-----------------------");
    
        Console::WriteLine(L"Enter the Type of Flower Order");
        Console::WriteLine(L"1. Roses");
        Console::WriteLine(L"2. Lilies");
        Console::WriteLine(L"3. Daisies");
        Console::WriteLine(L"4. Carnations");
        Console::WriteLine(L"5. Live Plant");
        Console::WriteLine(L"6. Mixed");
        Console::Write(L"Your Choice: ");
        type = int::Parse(Console::ReadLine());
    
        Console::WriteLine(L"Enter the Color");
        Console::WriteLine(L"1. Red");
        Console::WriteLine(L"2. White");
        Console::WriteLine(L"3. Yellow");
        Console::WriteLine(L"4. Pink");
        Console::WriteLine(L"5. Orange");
        Console::WriteLine(L"6. Blue");
        Console::WriteLine(L"7. Lavender");
        Console::WriteLine(L"8. Mixed");
        Console::Write(L"Your Choice: ");
        color = int::Parse(Console::ReadLine());
    
        Console::WriteLine(L"Enter the Type of Arrangement");
        Console::WriteLine(L"U. Bouquet");
        Console::WriteLine(L"V. Vase");
        Console::WriteLine(L"B. Basket");
        Console::WriteLine(L"M. Mixed");
        Console::Write(L"Your Choice: ");
        arrangement = __wchar_t::Parse(Console::ReadLine());
    
        Console::Write(L"Enter the Unit Price: ");
        price = double::Parse(Console::ReadLine());
    
        Console::Write(L"Enter Quantity:       ");
        qty = int::Parse(Console::ReadLine());
    
        CFlower ^ flr = gcnew CFlower(type, color, arrangement, price);
        order->Flower = flr;
        order->Quantity = qty;
    
        return order;
    }
    
    void ShowFlowerOrder(COrderProcessing ^ order)
    {
        Console::WriteLine(L"=======================");
        Console::WriteLine(L"==-=-=Flower Shop=-=-==");
        Console::WriteLine(L"-----------------------");
        Console::WriteLine(L"Flower Type:  {0}", order->Flower->Type);
        Console::WriteLine(L"Flower Color: {0}", order->Flower->Color);
        Console::WriteLine(L"Arrangement:  {0}", order->Flower->Arrangement);
        Console::WriteLine(L"Price:        {0:C}", order->Flower->UnitPrice);
        Console::WriteLine(L"Quantity:     {0}", order->Quantity);
        Console::WriteLine(L"Total Price:  {0:C}", order->GetTotalPrice());
        Console::WriteLine(L"=======================");
    }
    
    int main()
    {
        COrderProcessing ^ flower = CreateFlowerOrder();
        ShowFlowerOrder(flower);
    
        Console::WriteLine();
        return 0;
    }
  18. Execute the application and test it. Here is an example:
     
    =======================
    ==-=-=Flower Shop=-=-==
    -----------------------
    Enter the Type of Flower Order
    1. Roses
    2. Lilies
    3. Daisies
    4. Carnations
    5. Live Plant
    6. Mixed
    Your Choice: 2
    Enter the Color
    1. Red
    2. White
    3. Yellow
    4. Pink
    5. Orange
    6. Blue
    7. Lavender
    8. Mixed
    Your Choice: 4
    Enter the Type of Arrangement
    U. Bouquet
    V. Vase
    B. Basket
    M. Mixed
    Your Choice: B
    Enter the Unit Price: 65.85
    Enter Quantity:       3
    =======================
    ==-=-=Flower Shop=-=-==
    -----------------------
    Flower Type:  2
    Flower Color: 4
    Arrangement:  B
    Price:        $65.85
    Quantity:     3
    Total Price:  $197.55
    =======================
    
    Press any key to continue . . .
  19. Close the DOS window

Declaring a Boolean Variable

A variable is referred to as Boolean if it can hold a value that is either true or false. To declare a Boolean variable, you can use the bool keyword. Here is an example:

using namespace System;

int main()
{
    bool drinkingUnderAge;

    return 0;
}

Alternatively, you can declare a Boolean variable using the Boolean data type. The Boolean data type is part of the System namespace. Here is an example:

using namespace System;

int main()
{
    bool drinkingUnderAge;
    Boolean TheFloorIsCoveredWithCarpet;

    return 0;
}

To display the value of a Boolean variable on the console, you can type its name in the parentheses of the Write() or the WriteLine() methods of the Console class. After the variable has been declared, the compiler initializes it with a false value. This can be demonstrated in the following program:

using namespace System;

int main()
{
    bool drinkingUnderAge;

    Console::WriteLine(L"Drinking Under Age: ");
    Console::WriteLine(drinkingUnderAge);

    return 0;
}

This would produce:

Drinking Under Age: False
Press any key to continue . . .

As you can see, by default, a Boolean variable is initialized with false when it is declared. You can initialize the variable with true or false to make sure you know its initial value. Here is an example:

using namespace System;

int main()
{
    bool drinkingUnderAge = true;

    Console::WriteLine(L"Drinking Under Age: ");
    Console::WriteLine(drinkingUnderAge);

    return 0;
}

At any time and when you judge it necessary, you can change the value of the Boolean variable by assigning it a true or false value. Here is an example:

using namespace System;

int main()
{
    bool drinkingUnderAge = true;

    Console::WriteLine(L"Drinking Under Age: ");
    Console::WriteLine(drinkingUnderAge);

    drinkingUnderAge = false;

    Console::WriteLine(L"Drinking Under Age: ");
    Console::WriteLine(drinkingUnderAge);

    return 0;
}

This would produce:

Drinking Under Age: True
Drinking Under Age: False
Press any key to continue . . .

Retrieving the Value of a Boolean Variable

As reviewed for the other data types in Lesson 8, you can request the value of a Boolean variable from the user. In this case, the user must type either True (or true) or False (or false) and you can retrieve it using the Read() or the ReadLine() methods of the Console class. Here is an example:

using namespace System;

int main()
{
    bool drivingUnderAge = false;

    Console::WriteLine(L"Were you driving under age?");
    Console::Write(L"If Yes, enter True. Otherwise enter False: ");
    drivingUnderAge = bool::Parse(Console::ReadLine());

    Console::WriteLine(L"\nWas Driving Under Age: {0}\n", drivingUnderAge);

    return 0;
}

Here is an example of running the program:

Were you driving under age?
If Yes, enter True. Otherwise enter False: true

Was Driving Under Age: True

Press any key to continue . . .

In Windows programming, to expect the user to enter a specify a value of being true or false, the operating system provides a control named CheckBox.

Creating a Boolean Member Variable

Like the other types of variables we used in previous lessons, a Boolean variable can be a member of a class. You declare it like any other variable, using the bool keyword or the Boolean data type. Here is an example:

public ref class CHouse
{
public:
	__wchar_t TypeOfHome;
	int    Bedrooms;
	float  Bathrooms;
	Byte   Stories;
	bool   HasCarGarage;
	int    YearBuilt;
	double Value;
};

When initializing an object that has a Boolean variable as a member, simply assign true or false to the variable. In the same way, you can retrieve or check the value that a Boolean member variable is holding by simply accessing it. Here are examples:

using namespace System;

public ref class CHouse
{
public:
	__wchar_t TypeOfHome;
	int Bedrooms;
	float Bathrooms;
	Byte Stories;
	bool HasCarGarage;
	int YearBuilt;
	double Value;
};

int main()
{
	CHouse ^ condominium = gcnew CHouse;

	condominium->HasCarGarage = false;
	condominium->YearBuilt = 2002;
	condominium->Bathrooms = 1.5F;
	condominium->Stories = 18;
	condominium->Value = 155825;
	condominium->Bedrooms = 2;
	condominium->TypeOfHome = L'C';

	Console::WriteLine(L"Type of Home:        ");
	Console::WriteLine(condominium->TypeOfHome);
	Console::WriteLine(L"Number of Bedrooms:  ");
	Console::WriteLine(condominium->Bedrooms);
	Console::WriteLine(L"Number of Bathrooms: ");
	Console::WriteLine(condominium->Bathrooms);
	Console::WriteLine(L"Number of Stories:   ");
	Console::WriteLine(condominium->Stories);
	Console::WriteLine(L"Year Built:          ");
	Console::WriteLine(condominium->YearBuilt);
	Console::WriteLine(L"Has Car Garage:      ");
	Console::WriteLine(condominium->HasCarGarage);
	Console::WriteLine(L"Monetary Value:      ");
	Console::WriteLine(condominium->Value);

	Console::WriteLine();
	return 0;
}

This would produce:

Type of Home:        C
Number of Bedrooms:  2
Number of Bathrooms: 1
Number of Stories:   18
Year Built:          2002
Has Car Garage:      False
Monetary Value:      155825

Press any key to continue . . .

Boolean Arguments

Like parameters of the other types, you can pass an argument of type bool or Boolean to a function. Such an argument would be treating as holding a true or false value.

When creating a Windows control, after using the control, it must be destroyed. In C++, this is traditionally done using the delete operator in the destructor of the parent or host of the control, which could be a form. Another detail of Windows controls is that they use or consume computer resources during their lifetime. When the controls are not used anymore, such as when their application closes, these resources should be freed and given back to the operating system to make them available to other applications. This task can be performed using the Dispose() method to the Control class, which can then be overridden by its child controls. The syntax of the Control.Dispose() method is:

protected: void Dispose(bool disposing);

This method takes one argument, disposing, that indicates how the resources would be released. If this argument is passed with a false value, only the unmanaged resources would be released. If it is passed as true, then both managed and unmanaged resources would be released.

During design, we saw that, if you have added a control to your application but you don't want that control anymore, you could delete it. In some rare cases, you may also want to allow the user to delete a control (instead of hiding it). When a control is deleted, the Control::ControlRemoved event is fired. The syntax of this event is:

public: event ControlEventHandler^ ControlRemoved;

This event is carried by a ControlEventHandler delegate through the ControlEventArgs class.

A Boolean Property

A property can be created as a Boolean type. To do this, first specify its data type as bool. When treating the property, make sure its get() accessory returns a Boolean type. If its a write property, make sure you pass a Boolean argument to its set() member.

Practical LearningPractical Learning: Creating a Boolean Property

  1. To create a Boolean property, change the Flower.h header file as follows:
     
    #pragma once
    
    public ref class CFlower
    {
    private:
        int    _tp;
        int    _clr;
        int    _arg;
        bool   _mx;
        double _price;
    
    public:
        property int Type
        {
            int get() { return _tp; }
            void set(int tp) { _tp = tp; }
        }
    
        property int Color
        {
            int get() { return _clr; }
            void set(int clr) { _clr = clr; }
        }
    
        property int Arrangement
        {
            int get() { return _arg; }
            void set(int arg) { _arg = arg; }
        }
    
        property bool Mixed
        {
    	bool get() { return _mx; }
    	void set(bool mx) { _mx = mx; }
        }
    
        property double UnitPrice
        {
            double get() { return _price; }
            void set(double price) { _price = price; }
        }
    
    public:
        CFlower(void);
        CFlower(int type, int color,
                int argn, bool mx, double price);
        ~CFlower();
    };
  2. Access the Flower.cpp source file and change it as follows:
     
    #include "Flower.h"
    
    CFlower::CFlower(void)
        : _tp(0), _clr(0),
          _arg(0), _mx(false),
          _price(45.95)
    {
    }
    
    CFlower::CFlower(int type, int color,
                     int argn, bool mx,
                     double price)
        : _tp(type),
          _clr(color),
          _arg(argn),
          _mx(mx),
          _price(price)
    {
    }
    
    CFlower::~CFlower()
    {
    }
  3. Save all

Enumerations

 

Introduction

Consider that, when creating a program for a real estate company that sells houses, you want the program to ask a customer the type of house that he or she wants to purchase and/or the type of garage that the desired house should have. Here is an example:

using namespace System;

int main()
{
	int TypeOfHouse  = 0;
	int TypeOfGarage = 0;

	Console::WriteLine(L"Enter the type of house you want to purchase");
	Console::WriteLine(L"1 - Single Family");
	Console::WriteLine(L"2 - Townhouse");
	Console::WriteLine(L"3 - Condominium");
	Console::Write(L"Your Choice: ");
	TypeOfHouse = int::Parse(Console::ReadLine());

	Console::WriteLine(L"Enter the type of garage you want");
	Console::WriteLine(L"0 - Doesn't matter");
	Console::WriteLine(L"1 - Interior");
	Console::WriteLine(L"2 - Exterior");
	Console::Write(L"Your Choice: ");
	TypeOfHouse = int::Parse(Console::ReadLine());

	Console::WriteLine(L"\nYou selected: {0}", TypeOfHouse);
	Console::WriteLine(L"Type of Garage: {0}", TypeOfGarage);

	return 0;
}

Here is an example of running the program:

Enter the type of house you want to purchase
1 - Single Family
2 - Townhouse
3 - Condominium
Your Choice: 1
Enter the type of garage you want
0 - Doesn't matter
1 - Interior
2 - Exterior
Your Choice: 2

You selected:   2
Type of Garage: 0
Press any key to continue . . .

 

For such a program, the numbers can be vague. 1 can be considered a general number but, in our program, it can represent a Single Family house or an Interior type of garage. At the same time, our program uses the constant 1 in particular meaningful ways. To make it possible to give more meaning to a constant number, when the number can be made part of a series, C++ allows you to create a type of list.

An enumerator is a series of constant integers that each has a specific position in the list and can be recognized by a meaningful name. Based on this, instead of just remembering that the constant 1 represents Single Family, you can create a list that has that type of house. In another list, instead of using 1 again, you can give it a name. Consequently, in each list, although the constant 1 would still be considered, at least it would mean something precise.

To create an enumerator, you use the enum keyword, followed by the name of the enumerator, followed by a name for each item of the list. The name of the enumerator and the name of each item of the list follows the rules we reviewed for names in C++. The formula of creating an enumeration is:

enum Series_Name {Item1, Item2, Item_n};

Here is an example:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };

	return 0;
}

After creating an enumerator, each item in the list is referred to as a member of the enumerator.

Indexing the Members of an Enumeration

Each member is assigned a constant number. The members are counted starting at 0, then 1, etc. By default, the first member in the enumerator is assigned the number 0, the second is 1, etc. This is referred to as the index. In fact, you can use Write() or WriteLine() to show the index of a member. This is illustrated in the following program:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
	Console::Write(L"Member Index: ");
	Console::WriteLine(Unknown);
	Console::Write(L"Member Index: ");
	Console::WriteLine(SingleFamily);
	Console::Write(L"Member Index: ");
	Console::WriteLine(TownHouse);
	Console::Write(L"Member Index: ");
	Console::WriteLine(Condominium);

	return 0;
}

This would produce:

Member Index: 0
Member Index: 1
Member Index: 2
Member Index: 3
Press any key to continue . . .

In this HouseType enumeration, the Unknown member has an index 0. The SingleFamily member has an index of 1. The TownHouse member has an index of 2.

You can specify or change the numbers to your liking when you create the enumeration but once the enumeration has been created, whether you specified these numbers or not, they cannot be changed.

To make the list start at a specific number, assign the starting value to the first item in the list. Here is an example:

using namespace System;

int main()
{
	enum HouseType { Unknown = 5, SingleFamily, TownHouse, Condominium };
	
	Console::Write(L"Member Index: ");
	Console::WriteLine(Unknown);
	Console::Write(L"Member Index: ");
	Console::WriteLine(SingleFamily);
	Console::Write(L"Member Index: ");
	Console::WriteLine(TownHouse);
	Console::Write(L"Member Index: ");
	Console::WriteLine(Condominium);

	return 0;
}

This would produce:

Member Index: 5
Member Index: 6
Member Index: 7
Member Index: 8
Press any key to continue . . .

This time, the Unknown member has a value of 5, the SingleFamily member has a value of 6, etc. When creating the enumeration, you can assign any value of your choice to any member of the enumeration, or you can set different ranges of values to various items. You can create a list like this:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium = 6 };
	
	Console::Write(L"Member Index: ");
	Console::WriteLine(Unknown);
	Console::Write(L"Member Index: ");
	Console::WriteLine(SingleFamily);
	Console::Write(L"Member Index: ");
	Console::WriteLine(TownHouse);
	Console::Write(L"Member Index: ");
	Console::WriteLine(Condominium);

	return 0;
}

This would produce:

Member Index: 0
Member Index: 1
Member Index: 2
Member Index: 6
Press any key to continue . . .

As mentioned already, you can assign any value to any member of the enumeration. You can even assign the same number to different members. Here are examples:

using namespace System;

int main()
{
	enum HouseType { Unknown = 4, SingleFamily, TownHouse = 12, Condominium };
	
	Console::Write(L"Member Index: ");
	Console::WriteLine(Unknown);
	Console::Write(L"Member Index: ");
	Console::WriteLine(SingleFamily);
	Console::Write(L"Member Index: ");
	Console::WriteLine(TownHouse);
	Console::Write(L"Member Index: ");
	Console::WriteLine(Condominium);

	return 0;
}

This would produce:

Member Index: 4
Member Index: 5
Member Index: 12
Member Index: 13
Press any key to continue . . .

We mentioned that an enumeration must be an integer type. This meant that the members can represent Byte, short, int, long or even char types. As we have demonstrated so far, by default, the members of an enumeration are of type int. When creating the elements of an enumeration, you can initialize them to specify the type of values that they would have. For example, if you want the members to be compared to character types, initialize them with single-quoted symbols. Here is an example:

public enum class FlowerArrangement
{
    Basket  = L'A',
    Bouquet = L'U',
    Vase    = L'V',
    Bundle  = L'D',
    Any
};

Notice you don't have to initialize all members, only those for whom you want to specify a specific value.

Declaring an Enumeration Variable

After creating an enumeration, it can be used as a data type and you can declare a variable from it. One of the formulas you can use is:

Series_Name VariableName;

Here is an example:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
	HouseType hType;

	return 0;
}

When you declare a variable using an enumerator, the variable is initialized to the value of the first member of the enumeration. To initialize a variable declared from an enumeration, assign the name of the desired member to the variable. Here is an example:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
	HouseType hType = SingleFamily;

	Console::Write(L"Enumerator: ");
	Console::WriteLine(hType);

	return 0;
}

This would produce:

Enumerator: 1
Press any key to continue . . .

As done with the other variables, you can declare more than one variable of an enumerator type. Here is an example:

using namespace System;

int main()
{
	enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
	HouseType hHouse = SingleFamily;
	HouseType apart  = Condominium;

	return 0;
}

Instead of declaring the variable(s) after the list has been created, you can declare the variables of the enumeration type on the right side of the list but before the closing semi-colon. Here is an example:

using namespace System;

int main()
{
	enum HouseType
	{
		Unknown,
		SingleFamily,
		TownHouse,
		Condominium
	} hHouse;
	
	hHouse = SingleFamily;
	HouseType apart  = Condominium;

	Console::Write(L"Enumerator: ");
	Console::WriteLine(hHouse);

	return 0;
}

You can also initialize he variable(s) when declaring it(them). Here is an example:

using namespace System;

int main()
{
	enum HouseType
	{
		Unknown,
		SingleFamily,
		TownHouse,
		Condominium
	} hHouse = SingleFamily, apart  = Condominium;

	Console::Write(L"Enumerator: ");
	Console::WriteLine(hHouse);

	return 0;
}

Global Enumerations

An enumeration is referred to as global when it is created outside of any function or class. For example, you can create an enumeration above main() to make it global:

using namespace System;

enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
int main()
{
	return 0;
}

After creating a global enumeration, you can use it as you see fit. For example, you can use it directly in your source code or you can declare its variable where you see fit. Here is an example:

using namespace System;

enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
int main()
{
	HouseType hType;

	return 0;
}

When we study functions, we will see that a global enumeration can be accessed from any function of the same source file.

Enumerations and Assemblies

By default, if you create an enumeration the way we have proceeded so far, it would be available only in the assembly it belongs to. Just we reviewed for a class, you can control an enumeration's accessibility outside of its assembly. This means that you can hide or make it visible outside of its assembly. To do this, you can precede it with the private or the public keyword. Here is an example:

using namespace System;

public enum HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
int main()
{
	HouseType hType;

	return 0;
}

Enumerations and Classes

 

An Enumeration as a Member Variable 

If you have created an enumeration, it has characteristics that resemble those of an integer type. This allows you to use it as a data type to declare a variable. To create a member variable that is of an enumeration type, follow the same rules as done for the primitive types: the name of the enumeration, followed by the name of the variable, and followed by a semi-colon. Here is an example:

public enum HouseType
{
	Unknown,
	SingleFamily,
	TownHouse,
	Condominium
};

public value class CHouse
{	
public:
	String ^ PropertyNumber;
	String ^ Address;
	String ^ City;
	String ^ State;
	String ^ ZIPCode;
	HouseType TypeOfHome;
	int Bedrooms;
	float Bathrooms;
	Byte Stories;
	bool HasCarGarage;
	int YearBuilt;
	int  Condition;
	__wchar_t Style;
	double Value;
};

In the same way, you can declare as many enumeration variables as you want. After declaring the variable, to initialize it, assign it the desired member of the enumeration. Here is an example:

int main()
{
	CHouse ^ home = gcnew CHouse;

	home->TypeOfHome = SingleFamily;

	. . .

	Console::WriteLine();
	return 0;
}

Once the member variable has been initialized, you can use it as you see fit as we will learn and practice in future lessons. At a minimum, you can pass it to Write() or WriteLine() to display its value. Here is an example:

using namespace System;

public enum HouseType
{
	Unknown,
	SingleFamily,
	TownHouse,
	Condominium
};

public value class CHouse
{	
public:
	String ^ PropertyNumber;
	String ^ Address;
	String ^ City;
	String ^ State;
	String ^ ZIPCode;
	HouseType TypeOfHome;
	int Bedrooms;
	float Bathrooms;
	Byte Stories;
	bool HasCarGarage;
	int YearBuilt;
	int  Condition;
	__wchar_t Style;
	double Value;
};

int main()
{
	CHouse ^ home = gcnew CHouse;

	home->PropertyNumber    = "288635";
	home->Address           = "6808 Lilas Drive";
	home->City              = "Silver Spring";
	home->State             = "MD";
	home->ZIPCode           = "20904";
	home->TypeOfHome        = SingleFamily;
	home->Bedrooms  = 5;
	home->Bathrooms = 1;
	home->Stories           = 3;
	home->HasCarGarage      = true;
	home->YearBuilt         = 1992;
	home->Condition         = 2;      // Good, may need minor repair
	home->Style             = L'M';   // High-rise
	home->Value             = 555825;

	Console::WriteLine(L"Property #:          {0}", home->PropertyNumber);
	Console::WriteLine(L"Address:             {0}", home->Address);
	Console::WriteLine(L"                     {0}", home->City);
	Console::WriteLine(L", ");
	Console::Write(home->State);
	Console::WriteLine(L" ");
	Console::WriteLine(home->ZIPCode);
	Console::WriteLine(L"Type of Home:        ");
	Console::WriteLine(home->TypeOfHome);
	Console::WriteLine(L"Number of Bedrooms:  {0}", home->Bedrooms);
	Console::WriteLine(L"Number of Bathrooms: {0}", home->Bathrooms);
	Console::WriteLine(L"Number of Stories:   {0}", home->Stories);
	Console::WriteLine(L"Has Car Garage:      {0}", home->HasCarGarage);
	Console::WriteLine(L"Year Built:          {0}", home->YearBuilt);
	Console::WriteLine(L"Condition:           {0}", home->Condition);
	Console::WriteLine(L"Style:               {0}", home->Style);
	Console::WriteLine(L"Property Value:      {0}", home->Value);

	Console::WriteLine();
	return 0;
}
You cannot use the data formatting features of the curly brackets such as {0} to display the value of an enumeration.

This would produce:

Property #:          288635
Address:             6808 Lilas Drive
                     Silver Spring, MD 20904
Type of Home:        SingleFamily
Number of Bedrooms:  5
Number of Bathrooms: 1
Number of Stories:   3
Has Car Garage:      True
Year Built:          1992
Condition:           2
Style:               M
Property Value:      555825

Press any key to continue . . .

An Enumeration as a Class

By default, if you declare a variable of an enumeration type in main(), it would get stored in the stack memory and the compiler would be in charge of "cleaning up" after it when the program exits. If you want, you can store the variable in the managed heap so the garbage collector would be in charge of it. To do this, when creating the enumeration, precede its name with struct or class. Here is an example:

public enum class HouseType { Unknown, SingleFamily, TownHouse, Condominium };

After creating the enumeration like this, you can use it as a data type and declare a variable of it.

 Here is an example:

using namespace System;

public enum class HouseType { Unknown, SingleFamily, TownHouse, Condominium };
	
int main()
{
	HouseType hType;

	return 0;
}

You can also use it to create a member variable of a class as we saw in the previous section. This time, you use a different technique to access the members of the enumeration. In reality, and as we will learn when we study static member variables, the members of the enumeration become static. To access a member of the enumeration, you must qualify it. To do this, type the name of the enumeration, followed by the :: operator, followed by the desired member of the enumeration. Here is an example:

using namespace System;

public enum class HouseType
{
	Unknown,
	SingleFamily,
	TownHouse,
	Condominium
};

public value class CHouse
{	
public:
	String ^ PropertyNumber;
	String ^ Address;
	String ^ City;
	String ^ State;
	String ^ ZIPCode;
	HouseType TypeOfHome;
	int Bedrooms;
	float Bathrooms;
	Byte Stories;
	bool HasCarGarage;
	int YearBuilt;
	int  Condition;
	__wchar_t Style;
	double Value;
};

int main()
{
	CHouse ^ home = gcnew CHouse;

	home->PropertyNumber    = L"288635";
	home->Address           = L"6808 Lilas Drive";
	home->City              = L"Silver Spring";
	home->State             = L"MD";
	home->ZIPCode           = L"20904";
	home->TypeOfHome        = HouseType::SingleFamily;
	home->Bedrooms  = 5;
	home->Bathrooms = 1;
	home->Stories           = 3;
	home->HasCarGarage      = true;
	home->YearBuilt         = 1992;
	home->Condition         = 2;      // Good, may need minor repair
	home->Style             = L'M';   // High-rise
	home->Value             = 555825;

	Console::WriteLine(L"Property #:          {0}", home->PropertyNumber);
	Console::WriteLine(L"Address:             {0}", home->Address);
	Console::Write(L"                     {0}", home->City);
	Console::Write(L", ");
	Console::Write(home->State);
	Console::Write(L" ");
	Console::WriteLine(home->ZIPCode);
	Console::Write(L"Type of Home:        ");
	Console::WriteLine(home->TypeOfHome);
	Console::WriteLine(L"Number of Bedrooms:  {0}", home->Bedrooms);
	Console::WriteLine(L"Number of Bathrooms: {0}", home->Bathrooms);
	Console::WriteLine(L"Number of Stories:   {0}", home->Stories);
	Console::WriteLine(L"Has Car Garage:      {0}", home->HasCarGarage);
	Console::WriteLine(L"Year Built:          {0}", home->YearBuilt);
	Console::WriteLine(L"Condition:           {0}", home->Condition);
	Console::WriteLine(L"Style:               {0}", home->Style);
	Console::WriteLine(L"Property Value:      {0}", home->Value);

	Console::WriteLine();
	return 0;
}

Practical LearningPractical Learning: Creating Enumerations

  1. To create a few enumerations, access the Flower.h header file and change it with the following:
     
    #pragma once
    
    public enum class FlowerType
    {
        Roses = 1,
        Lilies,
        Daisies,
        Carnations,
        LivePlant,
        Mixed
    };
    
    public enum class FlowerColor
    {
        Red = 1,
        White,
        Yellow,
        Pink,
        Orange,
        Blue,
        Lavender,
        Mixed
    };
    
    public enum class FlowerArrangement
    {
        Bouquet = 1,
        Vase,
        Basket,
        Mixed
    };
    
    public ref class CFlower
    {
        . . .
    
    };
  2. Save all

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