When a function's declaration exists in a class or a namespace but has no implementation yet, you can create definition (implementation) for that function using the Generate definition feature.
Generate a function definition
In the editor, place caret at the desired position.
To access the Generate definition action, do one of the following:
From the main menu, choose Generate Definitions in the dialog that opens.or press Alt+Insert, or choose and select
Right-click the mouse and select Generate from the context menu. In the dialog that opens select the Generate Definitions option.
In the dialog that appears, select the functions to generate definition for:
Click OK to apply.
The function's definition appears starting from the caret position. In case when the caret is placed inside a class, the functions body is added to the existing declarations.