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Returning a Tracking Reference
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As done for regular types, you
can return a tracking reference to a class.
To indicate this, type the % operator
between the class type and the name of the function. In the body of the function, you can create a
class as complete as possible, get a tracking reference to that class, and
return that reference. Here is an example:
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using namespace System;
public value class CCar
{
public:
String ^ Make;
String ^ Model;
int Doors;
int Year;
double Price;
};
CCar % Build();
int main()
{
CCar ^ vehicle = Build();
Console::WriteLine(L"Car Characteristics");
Console::WriteLine(L"Make: {0}", vehicle->Make);
Console::WriteLine(L"Model: {0}", vehicle->Model);
Console::WriteLine(L"Doors: {0}", vehicle->Doors);
Console::WriteLine(L"Year: {0}", vehicle->Year);
Console::WriteLine(L"Value: {0:C}", vehicle->Price);
Console::WriteLine();
return 0;
}
CCar % Build()
{
CCar car;
Console::Write(L"Enter Make: ");
car.Make = Console::ReadLine();
Console::Write(L"Enter Model: ");
car.Model = Console::ReadLine();
Console::Write(L"# of Doors: ");
car.Doors = int::Parse(Console::ReadLine());
Console::Write(L"Year Made: ");
car.Year = int::Parse(Console::ReadLine());
Console::Write(L"Enter Price: ");
car.Price = double::Parse(Console::ReadLine());
CCar % veh = car;
return veh;
}
This would produce:
Enter Make: Honda
Enter Model: Accord
# of Doors: 4
Year Made: 1998
Enter Price: 14500
Car Characteristics
Make: Honda
Model: Accord
Doors: 4
Year: 1998
Value: $14,500.00
Press any key to continue . . .
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 Practical
Learning: Introducing Data Reading |
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- To start a new program, launch Microsoft Visual C++ 2005
- On the main menu, click File -> New -> Project...
- On the left side, make sure that Visual C++ is selected. In the Templates
list, click CLR Empty Project
- In the Name box, replace the string with RealEstate10 and click OK
- On the main menu, click Project -> Add New Item...
- To create a header file, in the Templates list, click Header File (.h)
- Set the Name to Property and click Add
- Complete the file as follows:
#pragma once
using namespace System;
namespace RealEstate
{
public ref class CProperty
{
public:
long PropertyNumber;
String ^ Address;
String ^ City;
String ^ State;
String ^ ZIPCode;
int Bedrooms;
float Bathrooms;
int YearBuilt;
double MarketValue;
};
}
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- To create another header file, on the main menu, click Project -> Add New Item...
- In the Templates list, make sure Header File (.h) is selected.
Set the Name to House and press Enter
- Complete the file as follows:
#pragma once
#include "Property.h"
using namespace System;
namespace RealEstate
{
public ref class CHouse : public CProperty
{
public:
Byte Stories;
int Condition;
unsigned NumberOfGarageSpaces;
};
}
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- To create one more header file, on the main menu, click Project -> Add New Item...
- In the Templates list, make sure Header File (.h) is selected.
Set the Name to SingleFamily and click Add
- Complete the file as follows:
#pragma once
#include "House.h"
using namespace System;
namespace RealEstate
{
public ref class CSingleFamily : public CHouse
{
public:
__wchar_t Style;
double LotSizeInSqFt;
};
}
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- To create a source file, on the main menu, click Project -> Add New
Item...
- In the Templates list, click C++ File (.cpp)
- In the New box, type Exercise and click Add
- In the empty file, type:
#include <iostream>
#include "SingleFamily.h"
using namespace std;
using namespace RealEstate;
int main()
{
String ^ strTitle1 = L"=//= Altair Realty =//=";
String ^ strTitle2 = L"-=- Properties Inventory -=-";
CSingleFamily ^ home = gcnew CSingleFamily;
Console::WriteLine(strTitle1);
Console::WriteLine(strTitle2);
Console::WriteLine();
return 0;
}
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- Execute the application to test it
- Close the DOS window
If you are defining a function and you want it to return a
handle to a class, you can. To indicate this, between the name of the class and
the name of the function, type the ^ operator.
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Practical
Learning: Returning a Handle |
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- To return a handle, change the Exercise.cpp file as follows:
#include <iostream>
#include "SingleFamily.h"
using namespace std;
using namespace RealEstate;
CSingleFamily ^ CreateListing()
{
CSingleFamily ^ home = gcnew CSingleFamily;
Console::WriteLine("To create a listing, enter the following information");
Console::Write("Property #: ");
home->PropertyNumber = long::Parse(Console::ReadLine());
Console::WriteLine("Property Condition");
Console::WriteLine("0. Unknown");
Console::WriteLine("1. Excellent");
Console::WriteLine("2. Good (may need minor repair");
Console::WriteLine("3. Acceptable (needs major repair)");
Console::WriteLine("4. Even (land is more important)");
Console::Write("Your Choice: ");
home->Condition = int::Parse(Console::ReadLine());
Console::Write("Street Address: ");
home->Address = Console::ReadLine();
Console::Write("City: ");
home->City = Console::ReadLine();
Console::Write("State: ");
home->State = Console::ReadLine();
Console::Write("ZIP Code: ");
home->ZIPCode = Console::ReadLine();
Console::Write("Bedrooms: ");
home->Bedrooms = int::Parse(Console::ReadLine());
Console::Write("Bathrooms: ");
home->Bathrooms = float::Parse(Console::ReadLine());
Console::Write("Stories: ");
home->Stories = int::Parse(Console::ReadLine());
Console::Write("Year Built: ");
home->YearBuilt = int::Parse(Console::ReadLine());
Console::WriteLine("Style");
Console::WriteLine("U. Unknown");
Console::WriteLine("S. Split Level");
Console::WriteLine("C. Colonial");
Console::WriteLine("G. Georgial");
Console::Write("Your Choice: ");
home->Style = __wchar_t::Parse(Console::ReadLine());
Console::Write("Garage Spaces: ");
home->NumberOfGarageSpaces = int::Parse(Console::ReadLine());
Console::Write("Total Lot Size: ");
home->LotSizeInSqFt = double::Parse(Console::ReadLine());
Console::Write("Market Value: ");
home->MarketValue = double::Parse(Console::ReadLine());
return home;
}
int main()
{
String ^ strTitle1 = L"=//= Altair Realty =//=";
String ^ strTitle2 = L"-=- Properties Inventory -=-";
CSingleFamily ^ house = CreateListing();
system("cls");
Console::WriteLine(strTitle1);
Console::WriteLine(strTitle2);
Console::WriteLine("=//= Property Listing =//=");
Console::WriteLine("Property #: {0}", house->PropertyNumber);
Console::WriteLine("Address: {0}\n {1}, {2} {3}",
house->Address, house->City,
house->State, house->ZIPCode);
Console::WriteLine("Condition: {0}", house->Condition);
Console::WriteLine("Style: {0}", house->Style);
Console::WriteLine("Bedrooms: {0}", house->Bedrooms);
Console::WriteLine("Bathrooms: {0}", house->Bathrooms);
Console::WriteLine("Stories: {0}", house->Stories);
Console::WriteLine("Year Built: {0}", house->YearBuilt);
Console::WriteLine("Garage Spaces: {0} SqFt",
house->NumberOfGarageSpaces);
Console::WriteLine("Lot Size: {0:F}", house->LotSizeInSqFt);
Console::WriteLine("Market Value: {0:C}", house->MarketValue);
Console::WriteLine();
return 0;
}
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- Execute the application to test it
- Close the DOS window
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