angular – Angualr2错误：无法设置仅具有getter的#的属性值

<form [ngFormModel]="myForm" (ngSubmit)="update()">

                <ion-label floating>First Name</ion-label>
                <ion-input type="text" id="fname" [ngFormControl]="fname"> 

   </form>

相关课程：

export class ProfilePage {
    myForm: ControlGroup;
    fname: AbstractControl;

    constructor(private _profile: Profile,fb: FormBuilder)  {

        this.myForm = fb.group({
            'fname': ['',Validators.compose([Validators.required,Validators.minLength(2),firstCharacter])]
        });

        this.fname = this.myForm.controls['fname'];


        Promise.all([this._profile.firstname,this._profile.lastname,this._profile.base64Image]).then(values => {
            this.fname.value = values[0];
         //   this.lname.value = values[1];

        });
    }

收到错误：

EXCEPTION: Error: Uncaught (in promise): TypeError: Cannot set property value of #<AbstractControl> which has only a getter