Getting error when creating property in Angular 2

Question

 I am trying to build a form using form controller

 

 

registerForm = new FormGroup

Here am getting registerForm property cannot find..please help me am new to this

 

import { Component, OnInit } from '@angular/core';

import{FormGroup, FormControl}from '@angular/forms'

@Component({

selector: 'my-app',

templateUrl:'app.component.html'

})

export class AppComponent implements OnInit//error here

{

ngOninit()

{

registerForm = new FormGroup({//error

first_name: new FormControl(),

last_name: new FormControl(),

phone: new FormControl(),

email: new FormControl(),

address: new FormGroup({

street: new FormControl(),

zip: new FormControl(),

city: new FormControl()

})

});

}

}