Victor R.

Posted on Feb 7, 2019

Nested FormArrays in Angular ReactiveForms

#angular #formarray #nesting #reactiveforms

Feb 7, 2019

Angular Reactive Forms with lots of Nesting

I looked everywhere for a solution I could just copy and paste into my project but with no luck, so here's my attempt at providing it for the next poor soul stuck in my situation. I've tried to keep the code as simple as possible.

You have a league

league_details: this.fb.group({
        name: "",
        founder: ""
      })

A league has teams

this.leagueForm = this.fb.group({
      league_details: this.fb.group({
        name: "",
        founder: ""
      }),
      teams: this.fb.array([this.teams])
    });

Teams have names and players

get teams(): FormGroup {
    return this.fb.group({
      team_name: "",
      players: this.fb.array([this.players])
    });
  }

Players have names and numbers

get players(): FormGroup {
    return this.fb.group({
      player_name: "",
      player_number: ""
    });
  }

You have a FormGroup

<form [formGroup]="leagueForm">

Show League Detail

<div class="form-header" formGroupName="league_details">
    <label>League Name <input formControlName="name"/></label>
    <label>Founder <input formControlName="founder"/></label>
  </div>

Show Teams

It's VITAL you have a wrapping div that defines formArrayName!

<div formArrayName="teams">
    <div class="teams" *ngFor="let team of leagueForm.get('teams').controls;
             let teamIndex = index" [formGroupName]="teamIndex">
      <label>Team Name <input formControlName="team_name"/></label>
      <!--  div with formArrayName='players' goes here (see below) -->
    </div>
</div>

Show Players inside Teams

Again, important you have a wrapping div with formArrayName. Also, you need to add players in context of the team. Notice in ngFor i am referencing the team variable
defined in the ngFor loop above for teams. I will also need to reference this team when removing or adding players.

Also notice the <span> element, this is how you reference the field for validation functionality.

<div formArrayName="players">
    <div class="players" *ngFor="let player of team.get('players').controls;
        let playerIndex=index" [formGroupName]="playerIndex">
        <label>Player Name <input formControlName="player_name" />
        <label>Player Number <input formControlName="player_number"/></label>
        <span *ngIf="player.get('player_number').touched">touched!</span>
    </div>
</div>

Adding Teams

Place ADD button just above the div that defines the formArrayArrayName teams

 <button type="button" (click)="addTeam()">Add Team</button>

addTeam() {
    (this.leagueForm.get("teams") as FormArray).push(this.teams);
  }

Adding Players

Place ADD button just above the div that defines the formArrayName players, and remember to pass in the team variable from the enclosing ngFor loop.

<button type="button" (click)="addPlayer(team)">Add Player</button>

addPlayer(team) {
    team.get("players").push(this.players);
  }

See project here on github:
https://github.com/crazedVic/angularnestedformarrays

Top comments (12)

Daniel Willis • Nov 30 '20

Thanks, this example is great - exactly what I needed.
One small thing I discovered was that the template didn't like iterating over the controls.

I had to change this:

let player of team.get('players').controls

to this:

let player of team.get('players')['controls']

Sym313 • Jan 7 '20 • Edited

Sadly doing all this, the .value of my form shows that player_name and player_number are not getting the data from the inputs. I had this problem with other examples. And I came here wishing to solve this issue. Any idea?

EDIT: If I copy your example without any more, works perfectly. I'll examine again my code.

Nawaf • Apr 30 '20

great walkthrough. In my case, I have a command form with a list of commands (e.g., subcommands). Each subcommand can have multiple subcommands,..., etc. Essentially, all commands use the same form but each need to keep track/be aware of their parent and children. I tried different solutions but I couldn't solve it. Any thoughts? thanks