从订阅打字稿返回值

Question

我如何从Save() 方法返回成功。

public SaveItem() {
 if(save()){ // The goal is to use save method like this
  // Close pop up;
}

public SaveAndNew() {
 if(save()){  // The goal is to use save method like this
  // Create new item;
}


private save() {
 let issuccess = false;

 this.myservice.AddParty(newUserObject)
  .subscribe(data => {   
    if (data['status'].toString() === '1') {
      return issuccess = false;
    } else {
      return issuccess = true;
    }
  },
    (er) => {

      return issuccess = false;
    });
}

• 如果我有save(): boolean，它将抛出Must return a value 的错误，如果在订阅之外返回issuccess，它将始终返回一个错误值。

我将如何等待保存功能并根据响应返回特定值？

我读过关于回调的文章，它似乎并不优雅，有没有优雅的方法来做到这一点

callbacks-vs-promises-vs-rxjs-vs-async-awaits

如果它是 C#，我会这样做

var isSuccess = await SaveAsync(party);

Answer 1

在这种情况下，您可以使用promise 而不是subscribe。但是在将数据绑定到 html 时，你应该使用async pipe

所以，你的服务会是这样的

 AddParty(newUserObject) {
        return this.http.post(url)
            .toPromise().then(responce => <any[]>responce.json())
            .catch(error => {
                return error;
            });
    }

并检索看起来像

this.myservice.AddParty(newUserObject)
            .then(data => {
                if (data['status'].toString() === '1') {
                    return issuccess = false;
                } else {
                    return issuccess = true;
                }
            },
            (er) => {

                return issuccess = false;
            });
    }

Answer 2

这样的事情怎么样：

public SaveItem() {
 const isNew = false;
 save(isNew)
}

public SaveAndNew() {
 const isNew = true;
 save(isNew)
}


private save(isNew) {

 this.myservice.AddParty(newUserObject)
  .subscribe(data => {   
    if (data['status'].toString() === '1') {
      saveComplete(isNew);
    } else {
      saveFailed(isNew)
    }
  },
    (er) => {
      saveFailed(isNew)
    });
}

saveComplete(isNew) {
  // Check isNew as needed.
  // Close dialog or whatever
}

saveFailed(isNew) {
  // do whatever here
}

或者 ... TypeScript 现在支持 async/await ... 所以你可以考虑在这里使用它们。更多信息请参见：https://medium.com/@benlesh/rxjs-observable-interop-with-promises-and-async-await-bebb05306875

Answer 3

你可以让你的保存方法返回一个可观察的布尔值

public SaveAndNew() {

this.save().subscribe(success =>
{
    if(success)
    {
      // Create new item;
    }
});

private save() : Observable<boolean> {

 return this.myservice
            .AddParty(newUserObject)
            .map(data=> data['status'].toString() === '1')
            .catch(err => Observable.of(false)); 
}

Answer 4

试试看

public SaveItem() {
 if(save()){ // The goal is to use save method like this
  // Close pop up;
}

public SaveAndNew() {
 if(save()){  // The goal is to use save method like this
  // Create new item;
}


private async save() {
 let issuccess = false;

await  this.myservice.AddParty(newUserObject)
  .subscribe(data => {   
    if (data['status'].toString() === '1') {
      return issuccess = false;
    } else {
      return issuccess = true;
    }
  },
    (er) => {

      return issuccess = false;
    });
      return issuccess ;
}

Answer 5

我们在 subscribe() 中在 er 操作之后有另一个操作参数，可以帮助您在不使用 observable 的情况下返回。

  public SaveItem() {
     if(save()){ // The goal is to use save method like this
      // Close pop up;
    }

    public SaveAndNew() {
     if(save()){  // The goal is to use save method like this
      // Create new item;
    }


    private save() {
     let issuccess = false;

     this.myservice.AddParty(newUserObject)
      .subscribe(data => {   
        if (data['status'].toString() === '1') {
          issuccess = false;
        } else {
          issuccess = true;
        }
      },
        (er) => {

          issuccess = false;
        },
     () => {return issuccess });
    }

订阅 3 个参数

subscribe(next?: (value: T) => void, error?: (error: any) => void, complete?: () => void):