What is the best way to iterate over an Angular HTTP Response?

Question

What is the best way to iterate over an Angular HTTP Response?

As a newcomer to Angular, I am working on mastering the process of uploading files and calling an API for validation. The API responds with a list of JSON validation errors based on specific file values.

I am currently struggling to iterate through these responses and display them to the user effectively.

After experimenting with map/pipe/subscribe, I have found that the subscribe function provides the most insight into the values being returned. However, I am unsure how to display these values properly instead of [Object, Object].

In addition, I want to ensure that I am following best practices but feel uncertain about my approach in this situation.

https://i.stack.imgur.com/vh44e.png

https://i.stack.imgur.com/4bByQ.png

https://i.stack.imgur.com/lKecn.png

https://i.stack.imgur.com/IvF9J.png

What steps should I take once my POST code is returned?

this.httpClient.post(this.PartsAPIURL, formData, { headers: headers })
      .subscribe(event => {
        this.submissionResult = event;
        console.log(this.submissionResult);
        //what to do here?
    });

Furthermore, how can I integrate this with the HTML response?

<p>{{submissionResult}}</p>

Below are examples of failed attempts at handling the response:

An attempt to assign to an array variable

this.httpClient.post(this.PartsAPIURL, formData, { headers: headers })
      .subscribe(event => {
        //fails because the validationErrors and subcategoryErrors are not initialized properly
        this.UploadResponse.validationErrors = event["validation_errors"];
        this.UploadResponse.subcategoryErrors = event["subcategory_errors"];
        console.log(this.UploadResponse.validationErrors);
        console.log(this.UploadResponse.subcategoryErrors);
    });

A snippet that does not return anything - no console statements present

this.httpClient.post<PartsUploadResponse>(this.PartsAPIURL, formData, { headers: headers })
      .pipe(
        map(data => {
          console.log(data)
          this.UploadResponse.subcategoryErrors = data['subcategoryErrors'];
          this.UploadResponse.validationErrors = data['validationErrors'];
          console.log(this.UploadResponse);
        }));

Response class structure

export class PartsUploadResponse {
  public validationErrors: any;
  public subcategoryErrors:any;

}

Thank you for your support!

arrays angular typescript httpresponse angular-pipe

Answer 1

Answer №1

To ensure accurate responses, let's establish the response type for TypeScript compiler to detect mistakes:

type ErrorResponse = {
  subcategory_errors: ErrorList[],
  validation_errors: ErrorList[]
}

type ErrorList = {
  sheet: string,
  errors: string[]
}

You can store the error lists in local variables as shown below:

subcategoryErrors: ErrorList[] = [];
validationErrors: ErrorList[] = [];

ngOnInit() {
  this.httpClient.post(this.PartsAPIURL, formData, { headers: headers })
      .subscribe((data: ErrorResponse) => {
        this.subcategoryErrors = data.subcategory_errors;
        this.validationErrors = data.validation_errors;
    });
}

For iterating through an array and displaying HTML, utilize the *ngFor directive. Use ng-container to group multiple HTML elements without adding an additional div.

<h1>Subcategory Errors></h1>
<ng-container *ngFor="let errorList of subcategoryErrors">
  <h2>{{ errorList.sheet }}</h2>
  <p *ngFor="let error of errorList.errors">{{ error }}</p>
</ng-container>

<h1>Validation Errors></h1>
<ng-container *ngFor="let errorList of validationErrors">
  <h2>{{ errorList.sheet }}</h2>
  <p *ngFor="let error of errorList.errors">{{ error }}</p>
</ng-container>

Answer 2

To ensure accurate responses, let's establish the response type for TypeScript compiler to detect mistakes:

type ErrorResponse = {
  subcategory_errors: ErrorList[],
  validation_errors: ErrorList[]
}

type ErrorList = {
  sheet: string,
  errors: string[]
}

You can store the error lists in local variables as shown below:

subcategoryErrors: ErrorList[] = [];
validationErrors: ErrorList[] = [];

ngOnInit() {
  this.httpClient.post(this.PartsAPIURL, formData, { headers: headers })
      .subscribe((data: ErrorResponse) => {
        this.subcategoryErrors = data.subcategory_errors;
        this.validationErrors = data.validation_errors;
    });
}

For iterating through an array and displaying HTML, utilize the *ngFor directive. Use ng-container to group multiple HTML elements without adding an additional div.

<h1>Subcategory Errors></h1>
<ng-container *ngFor="let errorList of subcategoryErrors">
  <h2>{{ errorList.sheet }}</h2>
  <p *ngFor="let error of errorList.errors">{{ error }}</p>
</ng-container>

<h1>Validation Errors></h1>
<ng-container *ngFor="let errorList of validationErrors">
  <h2>{{ errorList.sheet }}</h2>
  <p *ngFor="let error of errorList.errors">{{ error }}</p>
</ng-container>

Answer 3

Answer №2

Initially, the code that incorporates pipe/map operators is accurate. However, it is important to note that these operators do not initiate a call to the api by default. To make the call, subscribing to the observable returned from the http post method is essential.

Upon subscribing to the observable retrieved from the http post, you will receive the object from the API which can then be bound to the html.

Here is an example of TypeScript code for reference:

this.httpClient.post<any>(this.PartsAPIURL, formData, { headers: headers })
      .subscribe(result=> {
        this.submissionResult = result;
        console.log(this.submissionResult);
        //additional actions needed here
    });

The issue of displaying 'object object' typically arises when there are errors in implementing the HTML layout effectively. The HTML structure needs to be configured properly in order to display all properties within the submissionResult object.

To exhibit the inner properties of the object correctly, specific elements should be added to the HTML markup as demonstrated below:

HTML representation:

<p *ngIf="submissionResult">
    <div *ngFor="let validErrors of submissionResult.validationErrors">
      <div *ngFor="let error of validErrors">
         <span>{{error}}</span>
     </div>
   </div>
</p>

Answer 4

Initially, the code that incorporates pipe/map operators is accurate. However, it is important to note that these operators do not initiate a call to the api by default. To make the call, subscribing to the observable returned from the http post method is essential.

Upon subscribing to the observable retrieved from the http post, you will receive the object from the API which can then be bound to the html.

Here is an example of TypeScript code for reference:

this.httpClient.post<any>(this.PartsAPIURL, formData, { headers: headers })
      .subscribe(result=> {
        this.submissionResult = result;
        console.log(this.submissionResult);
        //additional actions needed here
    });

The issue of displaying 'object object' typically arises when there are errors in implementing the HTML layout effectively. The HTML structure needs to be configured properly in order to display all properties within the submissionResult object.

To exhibit the inner properties of the object correctly, specific elements should be added to the HTML markup as demonstrated below:

HTML representation:

<p *ngIf="submissionResult">
    <div *ngFor="let validErrors of submissionResult.validationErrors">
      <div *ngFor="let error of validErrors">
         <span>{{error}}</span>
     </div>
   </div>
</p>

What is the best way to iterate over an Angular HTTP Response?

Answer №1

Answer №2

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