Angular 4 bind checkbox to array in *ngFor

Question

I would like to add an item to an array whenever a check box is checked in *ngFor I am looking for a neat way of doing this without too much code or using a component method. I know this used to be really easy in angular version 1

<tr *ngFor="let this_user of RoleUsers.Users">
    ...
    <input type="checkbox" class="custom-control-input" [(ngModel)]="UsersToRemove.Users[this_user.id]" /> <!--[(ngModel)]="" --> <!-- ng-false-value="expression"-->
    ..
</tr>

For this code I get the error ERROR TypeError: Cannot read property '13' of undefined so I think I am very close.

At the moment I am using the user ids to track the keys but if I could have a nice array. If this is not possible without a component method please provide an example.

Update I have managed to get this working with fewer code;

<input type="checkbox" class="custom-control-input" (change)="AddOrRemoveUser(this_user, $event.target.checked)" />

Then the method;

AddOrRemoveUserToRemove (user, checked) {
    console.log ("Remove or add: ", user, checked);
}

I think this this the quickest way to do it.

The UsersToRemove object looks like this;

class UsersToRemove {
    Users: any[];
    InAction: boolean = false;
}

This is attached to the actual component.

Answer 1

This worked for me but with too much code. Just to answer my question;

@Component({
    ...
})
export class RoleUsersComponent implements OnInit {
    ..
    UsersToRemove: UsersToRemove = new UsersToRemove
  constructor(
     ...
  ) {
        ...
  }

  ...

    AddOrRemoveUser (user, checked) {
        if (checked==true){
            this.UsersToRemove.AddUser(user)
        }else {
            this.UsersToRemove.RemoveUser(user)
        }
        console.log ("UsersToRemove: ", this.UsersToRemove.Users)
    }
}

class UsersToRemove {
    Users: any[];
    constructor( ) { this.Users = []; }
    InAction: boolean = false;
    AddUser (user): void {
        if (!this.UserExists(user)){
            this.Users.push(user);
        }
    }
    RemoveUser (user): void {
        for (var _i = 0; _i < this.Users.length; _i++) {
            if (this.Users[_i].id==user.id){
                this.Users.splice( _i, 1 )
            }
        }
    }
    UserExists (user): boolean {
        let exists = false;
        for (var _i = 0; _i < this.Users.length; _i++) {
            if (this.Users[_i].id==user.id){
                exists = true;
            }
        }
        return exists;
    }
}

Template:

<tr *ngFor="let this_user of RoleUsers.Users">
  ...
  <th scope="row" *ngIf="UsersToRemove.InAction">
    <label class="custom-control custom-checkbox mb-2 mr-sm-2 mb-sm-0">
      <input type="checkbox" class="custom-control-input" (change)="AddOrRemoveUser (this_user, $event.target.checked)" /> <!--[(ngModel)]="" --> <!-- ng-false-value="expression"-->
      <span class="custom-control-indicator"></span>
    </label>
  </th>
  ...
</tr>