TypeScript Interfaces Class Interface


Example

Declare public variables and methods type in the interface to define how other typescript code can interact with it.

interface ISampleClassInterface {
  sampleVariable: string;

  sampleMethod(): void;
  
  optionalVariable?: string;
}

Here we create a class that implements the interface.

class SampleClass implements ISampleClassInterface {
  public sampleVariable: string;
  private answerToLifeTheUniverseAndEverything: number;

  constructor() {
    this.sampleVariable = 'string value';
    this.answerToLifeTheUniverseAndEverything = 42;
  }

  public sampleMethod(): void {
    // do nothing
  }
  private answer(q: any): number {
    return this.answerToLifeTheUniverseAndEverything;
  }
}

The example shows how to create an interface ISampleClassInterface and a class SampleClass that implements the interface.