Question

在下面的代码中，getElements函数没有等待getSChema（）函数完成，它是异步运行的，我如何进行同步函数调用，我想等到getschema（）函数执行完成< / p>

getSChema()
  {
    this.getPdiSchema(this.ApplicationsComponent.selectedApplication)
    .subscribe((res: any) => { 
      console.log("res:"+res);
     this.resdata=res;
            }
          );
  }

    getElements() {  
        let elements:any[]; 
          let complexType:any[];  
          let sequence:any[];  
          let elements1:any[]; 
          let elements2:any[]; 
          let complexType1:any[];  
          let sequence1:any[];   
          let elementsArray: PdiSchemaBase<any>[] = [];

    this.getSChema(); //wait until getSchema execution is complete

         elements =  this.resdata["xs:schema"]["xs:element"]
         complexType = elements[0]["xs:complexType"];
         sequence = complexType[0]["xs:sequence"];
         elements1 = sequence[0]["xs:element"];
         complexType1 = elements1[0]["xs:complexType"];
         sequence1 = complexType1[0]["xs:sequence"];
         this.pdiElements = sequence1[0]["xs:element"];  
         let i=1;
         for (let element of this.pdiElements)
         {
             console.log("printing elements:"+i)
           if(element["$"].type !== undefined)
           {
             console.log("element.type:"+element["$"].type)
               elementsArray.push(new TextboxElements({
               key: element["$"].name,
               label: element["$"].name,                       
               required: true,
               order: i
             }))
           }
            i=i + 1;
         }                  
      return elementsArray.sort((a, b) => a.order - b.order);
      }

如果我添加一个Observable并订阅它，则无法从getElements返回值

getElements()
{

      let elementsArray: PdiSchemaBase<any>[] = [];   
      console.log("calling get schema:");     
      console.log("this.selectedApplication:"+this.ApplicationsComponent.selectedApplication);   
      this.getPdiSchema(this.ApplicationsComponent.selectedApplication)
      .subscribe((res: any) => { 
       console.log("res:"+res);
       //code here....
        }
      );
         // this return doens't seems to work
         return elementsArray.sort((a, b) => a.order - b.order);
  }

Answer 1

最好更改getSChema()以返回observable。

getSChema() {
    return this.getPdiSchema(this.ApplicationsComponent.selectedApplication);
}

然后在getElements()中您可以订阅它

getElements() {
    ...
    this.getSChema().subscribe((res: any) => {
        // code to execute once it's completed
    })
}

对评论的回应：

从getSChema()移除getElements()，而在您致电getElements()的地方使用以下内容：

this.getSChema().subscribe((res: any) => {
    this.resdata = res;
    this.elements = this.getElements();
});

Answer 2

如果你想返回return elementsArray.sort((a, b) => a.order - b.order);，你可以使用map而不是subscribe，即返回一个observable和期望结果可以订阅的方法，所以在某行中。 ...

getElements() {
  return this.getSchema()
    .map(res => {
      // do your stuff here, then....
      return elementsArray.sort((a, b) => a.order - b.order);
    });
}

正在调用getElements ...

的函数

myFunction() {
  this.getElements()
    .subscribe(data => console.log(data));
}

或者您也许可以直接致电getSchema()，我会这样做：）

角度同步函数调用

2 个答案: