Angular：如何转换数组中的值并在外部范围内获取值？

Question

在这里，在DynamicDatabase 类中，我从服务器获取值并在console.log(this.rootLevelNodes) // folder-1 folder-2 folder-3 folder-4 中看到在下面的代码中，但我希望这个值在数组中。然后在this.route 之外，我打印console.log(this.rootLevelNodes) // there I got null [] (this.rootLevelNodes) in function but I dont know why I got null result，但我还想要在数组格式结果中如何查看我下面的代码并帮助我？

@Injectable()
export class DynamicDatabase {

  rootLevelNodes: string[] = [];
  constructor(private route : ActivatedRoute, private userService : UserService){}
  upperFolderId;
  urlOfFolder;

  initialData(): DynamicFlatNode[] {

    this.route.params.subscribe(params => {

      this.upperFolderId = params['userid'];
      this.urlOfFolder = params['url']+'/'+this.upperFolderId;

      this.userService.getPatternMainFolder({'urlOfFolder' : this.urlOfFolder}).subscribe(
        (data) => {
          if(data != undefined && data != '' && data.payload != undefined && data.payload != ''){
            for(var i = 0 ; i < data.payload.length ; i++){
              this.rootLevelNodes = data.payload[i].folderName;
              console.log(this.rootLevelNodes); // folder-1
                                                   folder-2
                                                   folder-3
                                                   folder-4
                                                   <-- this type result I got

              // I want this type result 
              console.log(this.rootLevelNodes); // ['folder-1','folder-2','folder-3','folder-4']
            }
          }
        }
      )
    });

    console.log(this.rootLevelNodes);  // [] --> Here I result got null array

     // Here also I want this type result want
    console.log(this.rootLevelNodes); //  ['folder-1','folder-2','folder-3','folder-4']
    return this.rootLevelNodes.map(name => new DynamicFlatNode(name, 0, true));
  }

Answer 1

我会将单个函数分成两部分：

initialData() {
    this.route.params.subscribe(params => {
      this.upperFolderId = params['userid'];
      this.urlOfFolder = params['url']+'/'+this.upperFolderId;
      this.anotherFunction(this.urlOfFolder);
    });
  }

anotherFunction(data) {
    this.userService.getPatternMainFolder({'urlOfFolder' : data}).subscribe(
    (data) => {
     if(data != undefined && data != '' && data.payload != undefined && data.payload != ''){
    for(var i = 0 ; i < data.payload.length ; i++){
      this.rootLevelNodes.push(data.payload[i].folderName);
      console.log(this.rootLevelNodes);
    }
  }
  return this.rootLevelNodes;
  }
 )
}

Answer 2

用this.rootLevelNodes.push(data.payload[i].folderName);代替this.rootLevelNodes = data.payload[i].folderName;