Patch values to checkbox using patchValue in angular

Question

I'm trying to re-use my create-form to edit the values of the form. My checkbox is working as per requirement while creating a form. When I click on edit form, the values aren't patching to my checkbox. Below is my code which I have tried:

<div class="form-row">
  <div class="form-group col-sm-6">
    <label>Authorized To</label>
    <br>
    <label *ngFor="let choice of authorized; let i=index">
      <input type="checkbox" [value]="choice" (change)="onCheckChange($event)" [checked]="checkedVal"
          formArrayName="authorized" type="checkbox[class.invalid]="! formGrowLicense.controls['authorized'].valid && formGrowLicense.controls['authorized'].touched ">
                            {{choice}}
     </label>
    <div *ngIf="!formGrowLicense.controls['authorized'].valid && (formGrowLicense.controls['authorized'].touched || isSubmitted)">
      <div class="invalid-feedback" style="display: block;">Please enter authorized to</div>
    </div>

  </div>
</div>

ts

authorized: any = ['CULTIVATE', 'HARVEST', 'PROCESS']; //displaying list of checkbox
constructor() {
  this.formGrowLicense = this.formBuilder.group({
      businessName: ['', Validators.required], 
      authorized: new FormArray([], [Validators.required])
       });
   } 
 getGrowLicense(id) {
    this.httpService.getGrowLicenseById(id).subscribe(
      response => {
        this.patchGrowLicense(response);
        this.checkedVal = response.authorisedTo; // tried storing response in this variable  ['CULTIVATE','HARVEST']
      },

      (err: any) => console.log(err)
    );
  }
patch(licenseObj){
    this.formGrowLicense.patchValue({
      businessName:licenseObj.companyName,
      authorized: licenseObj.authorisedTo, // here i'm getting response ['CULTIVATE','HARVEST']. Need to patch these two values as checked in checkbox
      });
    }

 onCheckChange(event) {
    this.formArray = this.formGrowLicense.get(
      'authorized'
    ) as FormArray;

    /* Selected */
    if (event.target.checked) {
      console.log(event.target.value);
      // Add a new control in the arrayForm
      this.formArray.push(new FormControl(event.target.value));
    } else {
      /* unselected */
      // find the unselected element
      let i = 0;

      this.formArray.controls.forEach((ctrl: FormControl) => {
        if (ctrl.value == event.target.value) {
          // Remove the unselected element from the arrayForm
          this.formArray.removeAt(i);
          return;
        }

        i++;
      });
    }
  }

Answer 1

You has an FormArray of FormControls that takes values true/false and received and array of strings among a fixed array, so first you need transform the array received in an array of true/false

First approach

First we are going to create a Form with a formArray. As always we can manage a form array we need to create a getter that return our formArray

  //our getter formArray
  get authorizedArray()
  {
    return this.formGrowLicense.get('authorized') as FormArray
  }

  ngOnInit()
  { //we create the formArray
    this.formGrowLicense=new FormGroup({
      businessName:new FormControl(),
      authorized:new FormArray(this.authorized.map(x=>new FormControl(false)))
    })
  }

See that the way to create the formArray is using new FormArray(..here and array of formControls..) . And the way to create the formArray of formControls is "mapping" each element of the array "this.autorized" to a FormControl.

To manage in a series of inputs we using this.html

<form [formGroup]="formGrowLicense">
    <input formControlName="businessName">
    <!--we use formArrayName in a div-->
    <div formArrayName="authorized">
        <!--we iterate over autorizedArray.controls
           remember our getter of the formArray? -->
        <div *ngFor="let control of authorizedArray.controls;let i=index">
            <!--we use [formControlName]=i -->
            <label><input type="checkbox"  [formControlName]="i">{{authorized[i]}}</label>
        </div>
    </div>
</form>

As always, we check if it's all ok using (only for check) in the.html

<pre>
  {{formGrowLicense?.value|json}}
</pre>

See how we iterate over the formArrayControls, and use the index, to show in the label authorized[i]

Well, We know yet how control a form array, so the next question: how we feed the formArray with the values?

Remember that we received some like, eg

{
  businessName:'my business name'
  authorized:['CULTIVATE', 'PROCESS']
}

when we received the value in data we can use some like

   this.formGroupLicense.patchValue(
    {
     businessName:data.businessName,
     authorized:this.authorized.map(x=>data.authorized.indexOf(x)>=0)
    }

See how transform the "data.authorize" and array with 0,1,2 or 3 elements in an array of 3 elements that takes values true or false

Well, the last work we need is, in submit, use the values of the formArray (eg [true,false,false] to get an array of strings

submit(form)
{
   if (form.valid)
   {
        const data={
           businessName:form.value.businessName
           authorize:form.value.authorized.map(
              (x,index)=>x?this.authorized[index]:null)
              .filter(x=>x)
        }
        console.log(data) //<--here we has the data we send to the service
   }
}

Yes, we map the [true,false,false] to ['CULTIVATE',null,null] and filter and only want elements that are not null ['CULTIVATE']

Well, use pathValue is ok but why we not create a function that return a formGroup with the data we want

createFormGroup(data:any=null)
{
    data=data||{businessName:null,authorize:[]}
    return new FormGroup({
      businessName:new FormControl(data.businessName),
      authorized:new FormArray(this.authorized
        .map(x=>new FormControl(data.authorized.indexOf(x)>=0)))
    })
}

So, when we received the data the only thing we need is use

  this.formGroupLicense=this.createFormGroup(data)

Second approach

We has a form like

    this.formGrowLicense=new FormGroup({
      businessName:new FormControl(),
      authorized:new FormControl()
    })

YES. authorized is a FormControl that store an array. If you see the material multi checked is this approach. For this you can check this SO with use a custom formControl. Let me explain (I don't want a customFormControl)

We has an auxiliary array with two properties "name" and "value" we want to get some like eg

authorizedAux: any = [{name:'CULTIVATE',value:true}, 
                      {name:'HARVEST',value:false},
                      {name:'PROCESS',value:true}]

So we add a function

  setAutorized(data: string[]) {
    this.authorizedAux = this.authorized.map(x => ({
      name: x,
      value: data.indexOf(x) >= 0
    }));
  }

And another function parse

  parse() {
    const result=this.authorized
      .map((x, index) => (this.authorizedAux[index].value ? x : null))
      .filter(x => x);
    return result.length>0?result:null
  }

then we can has an html that use ngModel, ngModelChange and ngModelOptions to change the value of the FormControl

<form [formGroup]="form">
    <input formControlName="businessName">
        <div *ngFor="let control of authorizedAux">
            <label>
        <input type="checkbox"  
            [ngModel]="control.value"
            (ngModelChange)="control.value=$event;form.get('authorized').setValue(parse())"
            [ngModelOptions]="{standalone:true}"
      >{{control.name}}</label>
        </div>
</form>

Remember that, when received the data we need call to the function setAutorized

See the two approaches in the stackblitz