Angular – How to fix: Property has no initializer and is not definitely assigned in the constructor

How to reproduce it

@Input() parentData: string;

Error

Property 'parentData' has no initializer and is not definitely assigned in the constructor.

Solution #1

Add the ! because the input is expecting the value to be passed. In this case, there is no default value. The exclamation point is called the non-null assertion operator and it tells the TypeScript compiler that the value of this property won’t be null or undefined.

@Input() parentData!: string;

Solution #2

Use the ?.

@Input() parentData?: string;

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