What is the difference if I create something in constructor vs ngOnInit? [duplicate]

Question

I created a form by calling a function from the constructor

constructor(private userManagementService: UserManagementService, private fb:FormBuilder) { this.createForm(); } createForm(){ this.signupForm = this.fb.group({ firstName:['',Validators.required], lastName:['',Validators.required], email:['',Validators.required], password:['',Validators.required] }); }

I suppose I could also create the form in ngOnInit

constructor(private fb:FormBuilder) { } ngOnInit{ this.signupForm = this.fb.group({ firstName:['',Validators.required], lastName:['',Validators.required], email:['',Validators.required], password:['',Validators.required] }); }

}

What is the difference between the two approaches? Is one better than the other?

Please go through this link: stackoverflow.com/questions/35763730/… — nithalqb
– nithalqb, Commented Feb 9, 2018 at 9:31
I provided the answer in duplicate question instead that addresses your concerns, i.e. practical differences between those two methods. Hope this helps. — Estus Flask
– Estus Flask, Commented Feb 9, 2018 at 12:36
Sometimes I feel like people think Stackoverflow is Google search or something... — RockGuitarist1
– RockGuitarist1, Commented Feb 9, 2018 at 18:26

Vivek Doshi · Accepted Answer · 2018-02-09 09:29:26Z

Constructor :

The constructor method on an ES6 class (or TypeScript in this case) is a feature of a class itself, rather than an Angular feature. It’s out of Angular’s control when the constructor is invoked, which means that it’s not a suitable hook to let you know when Angular has finished initialising the component.

ngOnInit :

ngOnInit is purely there to give us a signal that Angular has finished initialising the component , The ngOnInit lifecycle hook is a guarantee that your bindings are readily available.

Here is the great article about it in detail : READ

There are lot more discussion upon this like :

Difference between Constructor and ngOnInit

https://blog.angularindepth.com/the-essential-difference-between-constructor-and-ngoninit-in-angular-c9930c209a42

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