Multiple Objects into HttpParams

Question

I have some categories in a formcontrol, I send them in an array of string like this:

[1,4,6]

And that is my actual code:

let categoryIds = new Array<String>()
this.selectedCategories.forEach((value: string, key: string) =>
  categoryIds.push(key))

let requestOptions = {
    params: new HttpParams()
        .set('title', this.createNewForm.controls['title'].value)
        .append('content', this.createNewForm.controls['content'].value)
        .append('categoryids', categoryIds.toString()),              
    withCredentials: true
}

But I want to send them as an array of objects, with the old version of angular Http I was able to do a foreach of the object and append every category. But I don't know how to get every category and make each one an append to params. I need to get like this:

...categoryId=1&categoryId=4&categoryId=6...

Answer 1

You can create object containing all parameters and pass this object to fromObject property of HttpParamOptons while creating HttpParams

let data={
   firstname:'xyz',
   lastname:'pqr'
}

let body=new HttpParams({fromObject:data})

this.http.post(URL, body, this.header).subscribe(data => {
 ....
}, error => {
 ....
})

Answer 2

You can use .append to append values to a parameter and give you the result you are looking for when dealing with an array of values. .set is used to set or replace a value for a parameter. So really you should be doing something more like the following:

let httpParams = new HttpParams()
  .set('title', this.createNewForm.controls['title'].value)
  .set('content', this.createNewForm.controls['content'].value);

categoryIds.forEach(id => {
  httpParams = httpParams.append('categoryId', id);
});

const requestOptions = {
  params: httpParams,
  withCredentials: true
};

---

It's not obvious, but the .append method does not mutate the HttpParams object it was called from but instead returns a new object. This is why we reassign httpParams in the example above. Also, .append can be called without first using .set to set the parameter.

Answer 3

May be this is what you are looking for

component file:

import { Component } from '@angular/core';
import { HttpParams } from '@angular/common/http';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})

export class AppComponent {

data = [
       {id:'_', title:'_', content:'_'},
       ....,
       ....
       ];

mainArr:any = [];

constructor(){}

getCategory(item){
    this.mainArr.push({title:item.title,content:item.content,categoryId:item.id});

   console.log('mainArr',this.mainArr);

   let requestOptions = {
        params: new HttpParams()
        .append('data', this.mainArr),
        withCredentials: true
    }

   console.log('requestOptions',requestOptions);
  }
}