Angular 4 - using objects for option values in a select list

user_1738579 0
Viewed 116573

I know that similar questions have been asked, but I've found none with a good answer. I want to create a select list in an Angular form, where the value for each option is an object. Also, I do NOT want to use 2 way data binding. e.g. if my Component has these fields:


    lUsers: any[] = [
        { Name: 'Billy Williams', Gender: 'male' },
        { Name: 'Sally Ride', Gender: 'female'}
        ];
    curUser: any;

I would like my HTML template to contain this:


    <select #selectElem (change)="setNewUser(selectElem.value)">
        <option *ngFor="let user of lUsers" [ngValue]="user">
            {{user.Name}}
        </option>
    </select>

With this code, though, my setNewUser() function receives the contents of the selected user's Name field. Why it picks that specific field, I have no idea. What I expect is that it would receive the "value" of the selected option, which I specifically set to a user object.

Note that I used ngValue instead of value in the option. That was by suggestion of others on SO. If I use value instead, what happens is that the object gets converted to the string '[Object object]', which is what setNewUser() receives, which is useless.

FYI, I'm working on Windows 10, using angular 4.0.0 with @angular/cli 1.1.2. Here is the setNewUser() method:


    setNewUser(user: User): void {

    console.log(user);
    this.curUser = user;
    } // setNewUser()

I am determining just what exactly is being passed to it both my logging it, and also including this on the template: <pre>{{curUser}}</pre>

angular-forms angular
6 Answers

I'm currently using [ngValue] and it stores objects just fine.

The explanation as to why you experienced issues using (change) instead of (ngModelChange) can be found in this question

So, since you've already used [ngValue], you probably want to do something like this, where you will only use one way binding in order to be able to use the ngModelChange directive:

<select (ngModelChange)="setNewUser($event)" (ngModel)="lUsers">
        <option *ngFor="let user of lUsers" [ngValue]="user">
            {{user.Name}}
        </option>
    </select>

And your ts file will capture the event and receive the User object without needing to track it by id, basically reusing your old method will be good enough:

setNewUser(user: User): void {
    console.log(user);
    this.curUser = user;
    }

UPDATE 16/06/2020:

Always depending on your use case you may need to use square brackets instead of round here: (ngModel)="lUsers. For the particular case the OP stated, round brackets was the right choice. A clear and detailed description of the difference between square/round and banana box can be found in this answer from Angular guru Günter Zöchbauer

user_56557670
user_5144570

ANGULAR 6 SIMPLY DO THIS

HTML

<div class="col-3" style="float:left;padding-left: 18px !important;">
      <label>Vehicle No.</label>
      <div *ngIf="gpsDevicesArray && gpsDevicesArray.length > 0">
            <select [ngModel]="selectedVehicle" style="padding: 7px;border-radius: 4px;"
                    (ngModelChange)="onVehicleNumberChange($event)">
                    <option *ngFor=" let device of gpsDevicesArray" [ngValue]="device">
                        {{device.vehicleNumber}}
                    </option>
            </select>
      </div>
</div>

TYPESCRIPT

// For intital Value ( put this line inside server calling function )

 this.selectedVehicle = gpsDevicesArray[0];

// listener

 onVehicleNumberChange(device) {
        console.log("selectedVehicle ====", device);
 }
user_34076290

HTML:

<select [formControl]="years">
 <option value="">Select</option>
 <option *ngFor="let year of yearsList" [ngValue]="year">{{year.value}}</option>
</select>

TS:

years = new FormControl('');
yearsList = [{id: 1, value: '2019'}, {id:2, value: '2020'}];

this.years.valueChanges.subscribe((year) => {
 console.log(year)
});

RESULT: you will get year object in console :)

user_128123630

You can use ngModel and ngValue

<select [(ngModel)]="curUser ">
    <option *ngFor="let user of lUsers" [ngValue]="user">
        {{user.Name}}
    </option>
</select>
user_42975130
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