javascript - typescript 在函数中传递变量

Question

Typescript 的新手并试图了解它。

以下是基本上生成三个随机数的代码，我使用它们从 json 中选择随机对象。

    @Injectable()
 export class TrackService {
     public drawn :number[]=[];

     constructor(private http: Http) {


     }
     public getRandomTrack(): Observable<Track[]> {
         this.generateRandomNumbers();
         console.log(this.drawn);  //this.drawn is available here 
         return this.http
         .get(API_ENDPOINT)
         .map(this.extractRandomData);
     }



     public extractRandomData(res: Response) {
         let body = res.json();        
         console.log(this.drawn); //undefined here

         var randomTrack = [];

         for(var i=0;i<this.drawn.length; i++){
             randomTrack.push(body.results[this.drawn[i]]);
         }

         return randomTrack;
     }


     private generateRandomNumbers(){
         var available = [];

         for (var i = 1; i<= 55; i++) {
             available.push(i);
         }

         for (var i = 0; i <3; i++) {
             var random = Math.floor((Math.random() * available.length));
             this.drawn.push(available[random]);
             available.splice(random, 1);
         }

         return this.drawn;
     }

正如您在 extractRandomData 中看到的，this.drawn 是未定义的，我如何将 this.drawn 传递到该函数以便我可以访问该数组。

请帮忙。

Answer 1

你必须绑定(bind)上下文:

 public getRandomTrack(): Observable<Track[]> {
     this.generateRandomNumbers();
     console.log(this.drawn);  //this.drawn is available here 
     return this.http
     .get(API_ENDPOINT)
     .map((v) => { this.extractRandomData(v) });
 }

参见 “this” cannot be used in typescript function (Angular) 了解更多详情。