Override
Method attribute; specifies that a method must override a virtual
Type typename Extends basename
In method declarations, Override can be used to indicate that this method is expected to override a Virtual or Abstract method from the base class. Then the compiler will show an error if the method does not override anything (only a non-static method can override a virtual or abstract method).
Use of Override is not mandatory to override a virtual or abstract method, it is highly recommended, as it will help prevent inadvertent errors (name/signature not matching).
Override can only be specified on the method declaration in the UDT block, but not on the method body, because it is just a compile-time check in the context of the inheritance hierarchy, and does not affect the method in any way.
Override is only recognized as a keyword at the end of member procedure declarations. It can still be used as identifier elsewhere.
Syntax
Type typename Extends basename
...
Declare Sub|Function|Operator|Property|Destructor ... ( [parameterlist] ) [As datatype] Override
...
End TypeDeclare Sub|Function|Operator|Property|Destructor ... ( [parameterlist] ) [As datatype] Override
...
Description
In method declarations, Override can be used to indicate that this method is expected to override a Virtual or Abstract method from the base class. Then the compiler will show an error if the method does not override anything (only a non-static method can override a virtual or abstract method).
Use of Override is not mandatory to override a virtual or abstract method, it is highly recommended, as it will help prevent inadvertent errors (name/signature not matching).
Override can only be specified on the method declaration in the UDT block, but not on the method body, because it is just a compile-time check in the context of the inheritance hierarchy, and does not affect the method in any way.
Override is only recognized as a keyword at the end of member procedure declarations. It can still be used as identifier elsewhere.
Example
Type A Extends Object
Declare Virtual Sub f1( )
Declare Virtual Function f2( ) As Integer
End Type
Type B Extends A
Declare Sub f1( ) Override
Declare Function f2( ) As Integer Override
End Type
Sub A.f1( )
End Sub
Function A.f2( ) As Integer
Function = 0
End Function
Sub B.f1( )
End Sub
Function B.f2( ) As Integer
Function = 0
End Function
Declare Virtual Sub f1( )
Declare Virtual Function f2( ) As Integer
End Type
Type B Extends A
Declare Sub f1( ) Override
Declare Function f2( ) As Integer Override
End Type
Sub A.f1( )
End Sub
Function A.f2( ) As Integer
Function = 0
End Function
Sub B.f1( )
End Sub
Function B.f2( ) As Integer
Function = 0
End Function
Differences from QB
- New to FreeBASIC
See also