sealed
sealed is a context sensitive keyword that can indicate:
A virtual member cannot be overridden.
A type cannot be used as a base type.
sealed is also valid when compiling for native targets (without /clr).
Remarks
See Override Specifiers and Native Compilations for more information.
You can detect at compile time if a type is sealed with __is_sealed (type). For more information, see Compiler Support for Type Traits.
sealed is a context-sensitive keyword. See Context-Sensitive Keywords for more information.
Example
This sample shows the effect of sealed on a virtual member:
// sealed_keyword.cpp
// compile with: /clr
interface struct I1 {
virtual void f();
virtual void g();
};
ref class X : I1 {
public:
virtual void f() {
System::Console::WriteLine("X::f override of I1::f");
}
virtual void g() sealed {
System::Console::WriteLine("X::f override of I1::g");
}
};
ref class Y : public X {
public:
virtual void f() override {
System::Console::WriteLine("Y::f override of I1::f");
}
/*
// the following override generates a compiler error
virtual void g() override {
System::Console::WriteLine("Y::g override of I1::g");
}
*/
};
int main() {
I1 ^ MyI = gcnew X;
MyI -> f();
MyI -> g();
I1 ^ MyI2 = gcnew Y;
MyI2 -> f();
}
X::f override of I1::f X::f override of I1::g Y::f override of I1::f
The following sample shows how to mark a class as sealed:
// sealed_keyword_2.cpp
// compile with: /clr
interface struct I1 {
virtual void f();
};
ref class X sealed : I1 {
public:
virtual void f() override {}
};
ref class Y : public X { // C3246 base class X is sealed
public:
virtual void f() override {}
};
Requirements
Compiler option: /clr