title: Typescript / Angular 2: Property is missing in type
body: <p>I'm still quite new to Typescript and have trouble wrapping my head around interfaces. As I understand an interface is a type description or a contract for a class. It allows me to define, which properties a class can have and of which type they are. I try to implement that, but always get this error:</p>
  
  <pre><code>error TS2420: Class 'ResultPage' incorrectly implements interface 'ResultPageInterface'.
  Property 'entries' is missing in type 'ResultPage'.
  </code></pre>
  
  <p>Here is the code for the interface</p>
  
  <pre><code>export interface ResultPageInterface {
    entries:Array&lt;any&gt;;
    page_number:number;
    page_size:number;
    total_entries:number;
  }
  
  export class ResultPage implements ResultPageInterface {}
  </code></pre>
  
  <p>And here the class where I want to use it.</p>
  
  <pre><code>import { Injectable } from '@angular/core';
  import { ResultPage } from '../interfaces/result-page.interface';
  
  @Injectable()
  export class SomeClass {
  
    constructor() {}
  
    buildPage(res:any): ResultPage {
      let page:ResultPage = new ResultPage();
      page.entries = res.data;
      page.page_number = res.pagination.page_number;
      page.page_size = res.pagination.page_size;
      page.total_entries = res.pagination.total_entries;
      return page;
    }
  
  }
  </code></pre>