Angular 2+ material mat-chip-list formArray 验证

Question

How do I validate that a mat-chip has been added to the mat-chip-list . I am using ReactiveForms. I have tried with the required validator.

The value can be a list of names, so I need to make sure that there is atleast 1 name in my list of names before I can submit the form. If the list is empty then mat-error should display the error message. Using the required validator makes the form invalid, regardless of adding names to the list.

EDIT: Reactive Forms

I have tried to make a custom validator, and I am now using Reactive Forms instead of Template driven forms, but I cannot get it to work. I have edited the below code to reflect my changes and I have created this https://stackblitz.com/edit/angular-4d5vfj

HTML

<form [formGroup]="myForm">
  <mat-form-field class="example-chip-list">
    <mat-chip-list #chipList formArrayName="names">
      <mat-chip *ngFor="let name of myForm.get('names').controls; let i=index;"
        [formGroupName]="i"
        [selectable]="selectable"
        [removable]="removable"
        (removed)="remove(myForm, i)">
        <mat-icon matChipRemove *ngIf="removable">cancel</mat-icon>
      </mat-chip>

       <input placeholder="Names"
          [matChipInputFor]="chipList"
          [matChipInputSeparatorKeyCodes]="separatorKeysCodes"
          [matChipInputAddOnBlur]="addOnBlur"
          (matChipInputTokenEnd)="add($event, asset)">
    </mat-chip-list>
    <mat-error>Atleast 1 name need to be added</mat-error>
  </mat-form-field>
</form>

TS

import {COMMA, ENTER} from '@angular/cdk/keycodes';
import {Component} from '@angular/core';
import {FormGroup, FormControl, FormBuilder, FormArray} from '@angular/forms';
import {MatChipInputEvent} from '@angular/material';

@Component({
  selector: 'chip-list-validation-example',
  templateUrl: 'chip-list-validation-example.html',
  styleUrls: ['chip-list-validation-example.css'],
})
export class ChipListValidationExample {
  public myForm: FormGroup;

  // name chips
  visible = true;
  selectable = true;
  removable = true;
  addOnBlur = true;
  readonly separatorKeysCodes: number[] = [ENTER, COMMA];

  // data
  data = {
    names: ['name1', 'name2']
  }

  constructor(private fb: FormBuilder) {
    this.myForm = this.fb.group({
      names: this.fb.array(this.data.names, this.validateArrayNotEmpty)
    });
  }

  initName(name: string): FormControl {
    return this.fb.control(name);
  }

  validateArrayNotEmpty(c: FormControl) {
    if (c.value && c.value.length === 0) {
      return { 
        validateArrayNotEmpty: { valid: false }
      };
    }
    return null;
  }

  add(event: MatChipInputEvent, form: FormGroup): void {
    const input = event.input;
    const value = event.value;

    // Add name
    if ((value || '').trim()) {
      const control = <FormArray>form.get('names');
      control.push(this.initName(value.trim()));
      console.log(control);
    }

    // Reset the input value
    if (input) {
      input.value = '';
    }
  }

  remove(form, index) {
    console.log(form);
    form.get('names').removeAt(index);
  }
}

Answer 1

The problem is that the chipList's errorState isn't set to true when the chipList's FormArray status is INVALID .

I'm facing the same problem and don't know why this isn't working out of the box or how this can be achieved implicitly with the chipList's form being a FormArray .

As a workaround you can listen to status changes from the FormArray and set the chipList's errorState manually:

@ViewChild('chipList') chipList: MatChipList;

ngOnInit() {
  this.myForm.get('names').statusChanges.subscribe(
    status => this.chipList.errorState = status === 'INVALID'
  );
}

https://stackblitz.com/edit/angular-4d5vfj-gywxjz

Answer 2

Unfortunately, it's not possible to use any of Angular's predefined validators because they are not designed to work with arrays. I manage to do it with the help of this article:

https://www.dev6.com/Angular_Material_Chips_with_Reactive_Forms_and_Custom_Validation

Answer 3

To be able to get the validation working on a mat-chip-list we have to bind both the mat-input and mat-chip-list with same FormControl like below

Working Stackblitz link here

 <form [formGroup]='group'> <mat-form-field class="example-chip-list"> <mat-chip-list #chipList required formControlName="newFruit"> <mat-chip *ngFor="let fruit of fruits" (removed)="remove(fruit)"> {{fruit.name}} <mat-icon matChipRemove>cancel</mat-icon> </mat-chip> <input placeholder="New fruit..." formControlName="newFruit" [matChipInputFor]="chipList" [matChipInputSeparatorKeyCodes]="separatorKeysCodes" [matChipInputAddOnBlur]="addOnBlur" (matChipInputTokenEnd)="add($event)" required> </mat-chip-list> <!-- add mat-error --> <mat-error *ngIf="group.controls.newFruit.hasError('required')">required!</mat-error> </mat-form-field> </form>

Answer 4

As demonstrated by this example by mmalerba , you can use two separate form controls: one for the mat-chip-list (this one should be the one with the required flag), and a different one for the input. Interestingly, you'll have to manually set the values of both on the addEvent:

<!-- ... -->
    <mat-chip-list #chipList formControlName="names" required>
    <!-- ... -->
    <input placeholder="Names"
        [formControlName]="name"
        [matChipInputFor]="chipList"
        [matChipInputSeparatorKeyCodes]="separatorKeysCodes"
        [matChipInputAddOnBlur]="addOnBlur"
        (matChipInputTokenEnd)="add($event, asset)">
    </mat-chip-list>
    <!-- ... -->

import {Validators} from '@angular/forms';

    # ...
    constructor(private fb: FormBuilder) {
        this.myForm = this.fb.group({
            names: [this.data.names, Validators.required],
            name: ['']
        });
    }

    # ...
    add(event: MatChipInputEvent, form: FormGroup): void {
      const input = event.input;
      const value = event.value;

      // Add name
      if ((value || '').trim()) {
        const control = <FormArray>form.get('names');
        control.push(this.initName(value.trim()));
        console.log(control);
      }

      // Reset the input value
      if (input) {
        input.value = '';
      }

      // update form control (necessary for correct validation)
      this.myForm.controls.name.setValue(null);
      this.myForm.controls.names.setValue(this.data.names);
    }

    # ...
}

Here's their stackblitz example

Answer 5

For somebody is facing with this problem. After many hours, I have found the root cause of the issue and the solution for it as is:

At function add, remove, select of chiplist, you need to use function setValue in reactive form to make the validation work.

For example:

  this.form.get('names').value.push('abc');
  this.form.get('names').setValue(this.form.get('names').value); // => this line of code will make the validation work