Variable defined, but the console says not

Issue

It's a simple alertController box, which create a checklist element. When I click on add, the function addCheck() of the class ChecksPage is called :

 export class ChecksPage implements OnInit {
  checkList: Check[] = [];

  constructor(private alertCtrl: AlertController) { }

  ngOnInit() {
  }

  addCheck(){
    this.alertCtrl.create({
      header: 'Nouvelle liste',
      inputs:[{
          name:'nom',
          placeholder: 'Nom'

      }],

      buttons:[
        {
          text: 'Annuler',
          role: 'cancel'
        },

        {
          text: 'Ajouter',
          handler: data => {
            if(typeof data.nom !=null){
              let newCheck: Check;
              newCheck.id = ''+this.checkList.length;
              newCheck.title = data.nom;
              this.checkList.push(newCheck);
            }
          }
      }]
  }).then(alertEl => alertEl.present());
  }

}

But, I have an error : the variable newCheck is undefined. Why ? Check is an interface :

    export interface Check{
  id: string;
  title: string;
}

Solution

You didn't init your variable, please do as follow:

const newCheck = {
    id: ''+this.checkList.length,
    title: data.nom
} as Check;

Answered By - Ernesto Schiavo