TypeScript interface with function

Question

How can I create an interface which holds functions. I have tried this:

interface ILeonardo {
  addState(state: ILeonardoState),
  addStates(arr: Array<ILeonardoState>)
}

interface ILeonardoState {
  name: string,
  url: string,
  verb: string,
  options: Array<{name: string, status: number, data?: any, delay?: number}>
} 

but then I can't add the return type of addState and addStates .

Answer 1

Try this (replace the return value that you need)

interface ILeonardo {
   addState(state: ILeonardoState): boolean;
   addStates(arr: Array<ILeonardoState>): void;
}

The function deceleration need to end with semicolon.

http://www.typescriptlang.org/Handbook#interfaces