Extract Interface refactoring

This refactoring helps create a new interface based on a selected type. JetBrains Rider suggests choosing members to be transferred to the new interface. After extraction, the original type is updated to implement the new interface.

If the current type already implements any interfaces, those interfaces can also be extracted into the new interface.

In the example below, the Color property and the Draw method of the Circle class are extracted to create a new interface:

            
class Circle
{
  public Point Center { get; private set; }
  public Color Color { get; private set; }
  public int Radius { get; private set; }

  public void Draw()
  {
    // draw...
  }
}

            
interface IShape
{
  Color Color { get; }
  void Draw();
}

class Circle : IShape
{
  public Point Center { get; private set; }
  public Color Color { get; private set; }
  public int Radius { get; private set; }

  public void Draw()
  {
    // draw...
  }
}

Extract an interface from a type

Select a type in one of the following ways:
- In the editor, place the caret at the name of a type.
- Select a type in the Solution Explorer.
- Select a type in the Structure window.
Do one of the following:
- Press Control+Alt+Shift+T and then choose Extract Interface.
- Choose Refactor | Extract Interface from the main menu.
The Extract Interface dialog will open.
Specify a name for the new interface and where it should be placed — in a new file or in the same file as the original type.
Select members that you want to transfer to the new interface. The list of members can contain:
- Members of the current type
- Members of base types that the selected type currently inherits/implements
- Interfaces that the selected type currently implements
To quickly select all public members, click Select Public Alt+P.
If you have selected members that reference other members, the latter are highlighted with red. Click Dependent to resolve the conflict, that is to select any members that depend on the currently selected members.
To apply the refactoring, click Next.
If no conflicts are found, JetBrains Rider performs the refactoring immediately. Otherwise, it prompts you to resolve conflicts.
Right after the refactoring has been completed, all changes that it makes anywhere, including other files, are registered as a single operation. So you can use the Undo action Control+Z to roll back all these changes with a single keystroke.

JetBrains Rider. Extracting interface from a class

Last modified: 30 September 2021