Receiving an empty response when fetching JSON data using HTTP protocol

Question

Receiving an empty response when fetching JSON data using HTTP protocol

As a newcomer to Angular2, I'm struggling to understand how http requests work in this framework. Despite following tutorials and experimenting with both promises and observables, I can't seem to get the json response to display in my component. The data just won't show up.

Here's my code:

  private doAction() {
    this.doHttpRequest().subscribe(
      data => this.content = data
    );
    this.content = JSON.stringify(this.content);
  }

  private doHttpRequest() {
    return this.http.get('http://jsonplaceholder.typicode.com/posts/1')
                    .catch(this.handleError);
  }

The variable this.content is linked to my template. When I trigger the doAction() method by clicking a button, I initially see an empty string in the template for a second, then it changes to [object Object] after another second.

Can anyone pinpoint what's causing this issue?

json http typescript angular

Answer 1

Answer №1

That's the intended behavior

  private performTask() {
    // send request to server and listen for response with observable
    this.sendHttpRequest().subscribe(
      // called when data is received from server
      data => this.result = data
    );
    // execute immediately after the request is made but before a response is received
    this.result = JSON.stringify(this.result);
  }

To correct it, modify as follows

  private performTask() {
    this.sendHttpRequest().subscribe(
      data => {
        //this.result = data;
        this.result = data.json());
      });
    );
  }

If you want certain code to run after receiving the data, it should be placed inside the subscribe(...) callback.

Answer 2

That's the intended behavior

  private performTask() {
    // send request to server and listen for response with observable
    this.sendHttpRequest().subscribe(
      // called when data is received from server
      data => this.result = data
    );
    // execute immediately after the request is made but before a response is received
    this.result = JSON.stringify(this.result);
  }

To correct it, modify as follows

  private performTask() {
    this.sendHttpRequest().subscribe(
      data => {
        //this.result = data;
        this.result = data.json());
      });
    );
  }

If you want certain code to run after receiving the data, it should be placed inside the subscribe(...) callback.

Answer 3

Answer №2

When dealing with asynchronous http requests, it is important to handle your logic based on the results within the subscribe() callback:

private performAction() {
  this.makeHttpRequest().subscribe(
    data => {
      this.content = data;
      // additional logic should be placed here
    }
  );
}

private makeHttpRequest() {
  return this.http.get('http://jsonplaceholder.typicode.com/posts/1')
                .map(res => res.json());
                .catch(this.handleError);
}

Answer 4

When dealing with asynchronous http requests, it is important to handle your logic based on the results within the subscribe() callback:

private performAction() {
  this.makeHttpRequest().subscribe(
    data => {
      this.content = data;
      // additional logic should be placed here
    }
  );
}

private makeHttpRequest() {
  return this.http.get('http://jsonplaceholder.typicode.com/posts/1')
                .map(res => res.json());
                .catch(this.handleError);
}

Answer 5

Answer №3

When making an HTTP call, the data is being returned as indicated by displaying "[object Object]" in the template. To view the JSON data in the template, you can utilize the json pipe like this:

Note: There is no requirement for "this.data = JSON.stringify(this.data);" in your code.

Answer 6

When making an HTTP call, the data is being returned as indicated by displaying "[object Object]" in the template. To view the JSON data in the template, you can utilize the json pipe like this:

Note: There is no requirement for "this.data = JSON.stringify(this.data);" in your code.

Receiving an empty response when fetching JSON data using HTTP protocol

Answer №1

Answer №2

Answer №3

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