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Properties 6

get me and set me!

 

 

What we have in this page?

 

  1. More On Indexed Properties

  2. Declaring and Using Static Properties

 

 

More On Indexed Properties

 

An indexed property typically exposes a data structure that is accessed using a subscript operator. A default indexed property allows the user to access the data structure via the class name, whereas a user-defined indexed property requires the user to specify the property name to access the data structure. The following example shows how to use default and user defined indexed properties.

 

// property keyword, indexed property

// compile with: /clr

#include "stdafx.h"

 

using namespace System;

 

public ref class myClass

{

   array<int>^ MyArr;

   public:

      // constructor, 7 is the array size

      myClass() { MyArr = gcnew array<int>(7); }

      // default indexer

      property int default[int]

      {

         int get(int index) { return MyArr[index]; }

         void set(int index, int value) { MyArr[index] = value; }

      }

      // user-defined indexer

      property int indexer1[int]

      {

         int get(int index) { return MyArr[index]; }

         void set(int index, int value) { MyArr[index] = value; }

      }

};

 

int main()

{

   myClass ^ MyC = gcnew myClass();

   // use the default indexer

   Console::WriteLine("default indexer");

   Console::Write("[ ");

   for (int i = 0; i < 7; i++)

   {

      MyC[i] = i;

      Console::Write("{0} ", MyC[i]);

   }

   Console::WriteLine("]");

   // use the user-defined indexer

   Console::WriteLine();

   Console::WriteLine("user-defined indexer");

   Console::Write("[ ");

   for (int i = 0; i < 7; i++)

   {

      MyC->indexer1[i] = i * 2;

      Console::Write("{0} ", MyC->indexer1[i]);

   }

   Console::WriteLine("]");

   return 0;

}

 

Output:

 

 

A program example that shows how to use default and user defined indexed properties

 

The following example shows how to call the default indexer through the this pointer.

// call the default indexer through this pointer

// compile with: /clr

#include "stdafx.h"

 

using namespace System;

 

value class Position

{

   public:

     Position(int x, int y) : position(gcnew array<int, 2>(100, 100))

     { this->default[x, y] = 1; }

     property int default[int, int]

     {

        int get(int x, int y) { return position[x, y]; }

        void set(int x, int y, int value) {}

     }

   private:

     array<int, 2> ^ position;

};

 

int main()

{

   return 0;

}

// No output

The following example shows how you can use DefaultMemberAttribute to specify the default indexer.

// This is the main DLL file.

// specify the default indexer

// compile with: /LD /clr

#include "stdafx.h"

#include "specify_default_indexer.h"

 

using namespace System;

 

[Reflection::DefaultMember("XXX")]

public ref struct Squares

{

  property Double XXX[Double]

  {

     Double get(Double data) { return data*data; }

  }

};

The following example uses the metadata created in the previous example.

// use the default indexer

// compile with: /clr

#include "stdafx.h"

using namespace System;

#using "specify_default_indexer.dll"

 

int main()

{

  Squares ^ square = gcnew Squares();

  System::Console::WriteLine("{0}", square[3]);

  return 0;

}

 

Output:

9

Declaring and Using Static Properties

 

The following program example shows how to declare and use a static property. A static property can only access static members of its class.

// more on property keyword

// compile with: /clr

#include "stdafx.h"

 

using namespace System;

 

ref class StaticProperties

{

  static int MyInt;

  static int MyInt2;

 

  public:

    static property int Static_Data_Member_Property;

    static property int Static_Block_Property

    {

      int get() { return MyInt; }

      void set(int value) { MyInt = value; }

   }

};

 

int main()

{

  StaticProperties::Static_Data_Member_Property = 100;

  Console::WriteLine("StaticProperties::Static_Data_Member_Property: {0}",                         StaticProperties::Static_Data_Member_Property);

   StaticProperties::Static_Block_Property = 200;

  Console::WriteLine("StaticProperties::Static_Block_Property: {0}", StaticProperties::Static_Block_Property);

  return 0;

}

 

Output:

A program example that shows how to declare and use a static property. A static property can only access static members of its class

 

 

 

 

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