Unable to pass response from httpclient post method to another custom function in Angular 4

Question

Unable to pass response from httpclient post method to another custom function in Angular 4

I've implemented the addUser(newUser) function in my sign-in.service.ts file like this:

addUser(newUser)
  {
    const httpOptions = {
      headers: new HttpHeaders({ 'Content-Type': 'application/json' })
    };
    let body = JSON.stringify(newUser);
    this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions).subscribe(res=>{
      console.log(res);
      return res;
    });
  }

The console output after execution is

{msg: "successfully added", status: 200}

. However, when I call the addUser(newUser) function from the sign-in.component.ts file using the code below:

  addUser()
  {
    console.log(this.first_name,this.last_name,this.userName,this.email);
    let newUser = {
      "first_name":this.first_name,
      "last_name":this.last_name,
      "username":this.userName,
      "email":this.email
    }
    console.log(this.signService.addUser(newUser));
  }

The console output shows undefined. Can someone explain why? Your assistance would be greatly appreciated. Thank you.

angular typescript httpclient angular4-httpclient

Answer 1

Answer №1

When using httpclient, it will return an observable and log the response in the subscribe method. This may cause issues in the component if the call is not completed properly. To address this, you can follow this approach:

addUser(newUser): Observable<any> {
  const httpOptions = {
    headers: new HttpHeaders({ 'Content-Type': 'application/json' })
  };
  let body = JSON.stringify(newUser);
  return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions);
}

// Utilize async/await to handle responses correctly
async addUser() {
  console.log(this.first_name, this.last_name, this.userName, this.email);
  let newUser = {
    "first_name":this.first_name,
    "last_name":this.last_name,
    "username":this.userName,
    "email":this.email
  }
  const dataReturned = await this.signService.addUser(newUser).toPromise();
  console.log(dataReturned);
}

If you prefer not to use async/await, you should subscribe to the observable in your component.ts file:

addUser() {
  console.log(this.first_name, this.last_name, this.userName, this.email);
  let newUser = {
    "first_name":this.first_name,
    "last_name":this.last_name,
    "username":this.userName,
    "email":this.email
  }
  this.signService.addUser(newUser).subscribe(d => console.log(d));
}

In the service file:

addUser(newUser): Observable<any> {
  const httpOptions = {
    headers: new HttpHeaders({ 'Content-Type': 'application/json' })
  };
  let body = JSON.stringify(newUser);
  return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions);
}

Answer 2

When using httpclient, it will return an observable and log the response in the subscribe method. This may cause issues in the component if the call is not completed properly. To address this, you can follow this approach:

addUser(newUser): Observable<any> {
  const httpOptions = {
    headers: new HttpHeaders({ 'Content-Type': 'application/json' })
  };
  let body = JSON.stringify(newUser);
  return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions);
}

// Utilize async/await to handle responses correctly
async addUser() {
  console.log(this.first_name, this.last_name, this.userName, this.email);
  let newUser = {
    "first_name":this.first_name,
    "last_name":this.last_name,
    "username":this.userName,
    "email":this.email
  }
  const dataReturned = await this.signService.addUser(newUser).toPromise();
  console.log(dataReturned);
}

If you prefer not to use async/await, you should subscribe to the observable in your component.ts file:

addUser() {
  console.log(this.first_name, this.last_name, this.userName, this.email);
  let newUser = {
    "first_name":this.first_name,
    "last_name":this.last_name,
    "username":this.userName,
    "email":this.email
  }
  this.signService.addUser(newUser).subscribe(d => console.log(d));
}

In the service file:

addUser(newUser): Observable<any> {
  const httpOptions = {
    headers: new HttpHeaders({ 'Content-Type': 'application/json' })
  };
  let body = JSON.stringify(newUser);
  return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions);
}

Answer 3

Answer №2

The service call in the component code is not properly handled.

// user.service.ts
createUser(newUser) {
    const httpOptions = {
        headers: new HttpHeaders({
            'Content-Type': 'application/json'
        })
    };
    let body = JSON.stringify(newUser);
    return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions)
}

// Component
addUser() {
    console.log(this.firstName, this.lastName, this.username, this.email);
    let newUser = {
        "firstName": this.firstName,
        "lastName": this.lastName,
        "username": this.username,
        "email": this.email
    }
    this.userService.createUser(newUser).subscribe(response => {
        console.log(response);
        return response;
    });
}

Answer 4

The service call in the component code is not properly handled.

// user.service.ts
createUser(newUser) {
    const httpOptions = {
        headers: new HttpHeaders({
            'Content-Type': 'application/json'
        })
    };
    let body = JSON.stringify(newUser);
    return this.httpclient.post('http://localhost:3000/api/signup', body, httpOptions)
}

// Component
addUser() {
    console.log(this.firstName, this.lastName, this.username, this.email);
    let newUser = {
        "firstName": this.firstName,
        "lastName": this.lastName,
        "username": this.username,
        "email": this.email
    }
    this.userService.createUser(newUser).subscribe(response => {
        console.log(response);
        return response;
    });
}

Answer 5

Answer №3

The reason for this issue is...

console.log operates synchronously, whereas your http service functions asynchronously. As a result, when console.log runs, your service is still waiting for the response, hence why it returns as undefined.

To address this, you need to implement either promises or observables.

Answer 6

The reason for this issue is...

console.log operates synchronously, whereas your http service functions asynchronously. As a result, when console.log runs, your service is still waiting for the response, hence why it returns as undefined.

To address this, you need to implement either promises or observables.

Unable to pass response from httpclient post method to another custom function in Angular 4

Answer №1

Answer №2

Answer №3

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