в 15:31, 26 мая 2010

2010-05-26T15:31:02Z

Admin: 1 версия

2010-05-26T12:05:29Z

1 версия

Новая страница

==Casting class==

<source lang="csharp">
#include "stdafx.h"
using namespace System;
ref class A {};
ref class B : public A {};
ref class C {};
void main()
{
Object ^v1 = gcnew A();
Object ^v2 = gcnew B();
Object ^v3 = gcnew C();
A ^a1 = gcnew A();
A ^a2 = gcnew B();
A ^a3 = dynamic_cast<A^>(v1); // downcast
A ^a4 = dynamic_cast<A^>(v2); // downcast
B ^b1 = gcnew B();
B ^b2 = dynamic_cast<B^>(v2); // downcast
B ^b4 = dynamic_cast<B^>(a2); // downcast

C ^c1 = gcnew C();
C ^c2 = dynamic_cast<C^>(v1); // Fails c2 = null. Miss match classes
C ^c3 = static_cast<C^>(v2); // c3 has invalid value of type B class
C ^c4 = safe_cast<C^>(v3); // downcast
C ^c5 = (C^)(v3); // downcast
}

</source>

==Casting from object==

<source lang="csharp">
#include "stdafx.h"
using namespace System;
using namespace System::Collections;
ref class Book{
public:
Book(){ }
Book(String^ _title) { Title = _title; }
property String^ Title;
};
int main(){
ArrayList^ theList = gcnew ArrayList();
theList->Add( gcnew Book("Men") );
Book^ book = safe_cast<Book^>( theList[0] );
Console::WriteLine(book->Title );
theList->Add( gcnew String("data"));
try{
book = safe_cast<Book^>( theList[1] );
}catch(InvalidCastException^ e){
Console::WriteLine("wrong type");
}
}

</source>

==Checking casts==

<source lang="csharp">
#include "stdafx.h"
using namespace System;
ref class Base {};
ref class Derived : Base {} ;
int main(){
Base^ b = gcnew Base();
Derived^ d = gcnew Derived();
try
{
d = safe_cast<Derived^>(b);
}
catch (InvalidCastException^ e)
{
}

d = dynamic_cast<Derived^>(b);
if (d == nullptr)
{
}
}

</source>

← Предыдущая	Версия 15:31, 26 мая 2010
(нет различий)

Visual C++ .NET/Class/Casting - История изменений

в 15:31, 26 мая 2010

Admin: 1 версия