CODEWITHSUNDEEP
angulartypescript2.0
Ali Shahzad
Ali Shahzad

Reputation: 5332

TypeScript strictNullChecks - Object is possibly 'null'

After enabling strictNullChecks with Angular 4.1.1, getting several errors for null checks. I have fixed bundles of them but unable to fix the same Object is possibly 'null' for this.form.get('username').value. Likewise others, I have tried the same but unable to fix the error.

if (this.form.get('username') != null) {
    body.append('username', this.form.get('username').value);
}

Upvotes: 15

Views: 19190

Answers (2)

Benoit B.
Benoit B.

Reputation: 3661

You really don't need to cast here. You actually never have to.

The most compact way to do it:

const username = this.form.get('username');
if (username) body.append('username', username.value);

Or in exit-early style:

const username = this.form.get('username');
if (!username) return;
# back to normal flow
body.append('username', username.value); // no complaint, username cannot be falsy, then it must be { value: string }

The compiler cannot infer that this.form.get('username') hasn't change between the null check and the time you use .value on it.

With a const variable, it can.

Upvotes: 3

yurzui
yurzui

Reputation: 214275

Try using Non-null assertion operator like

this.form.get('username')!.value; // notice !

Upvotes: 37

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