How to update controls of FormArray

Question

My form group code is as

this.myForm = this._fb.group({            
            branch_name: ['', [Validators.required]],
            branch_timing: this._fb.array([
                this.initBranchTiming(),
            ])                                
        });

initBranchTiming() {       
        return this._fb.group({
            day: ['', []],
            open_from: ['00:00:00', []],
            open_till: ['00:00:00', []]           
        });
  }

branch_name is updated by this code

(<FormControl>this.myForm.controls['branch_name']).updateValue(this.branch_detail.branch_name);

Now i have to update the 'day' field of form array. what to do to update the 'day' field of form array branch_timing ?

Answer 1

AFAIK putting a FormGroup inside of a FormArray strips the 'FormControls' of their names and makes it just a list, like a normal array.

In order to update the FormControls individually, you update the value of each AbstractControl from the FormGroup by using the index:

let index = 0; // or 1 or 2
(<FormArray>this.myForm.controls['branch_timing']).at(index).patchValue('example');

Or you can update the entire FormArray by calling setValue or patchValue:

(<FormArray>this.myForm.controls['branch_timing']).setValue(['example', 'example1', 'example2']);

setValue requires an array that matches the entire structure or the FormArray, while patchValue can take a super-set or sub-set of the array. (FormArray-class on Angular2's website)