TypeScript error: Type '() => boolean' is not assignable to type 'boolean'

Question

If array of user_list.length == 0, the "clear user" button should be disabled. When I am calling this.disabledButton function, it throws an error saying

Type '() => boolean' is not assignable to type 'boolean'

Below is my logic.

<section>
     <Button
        id='clear-user'
        disabled={this.disabledButton}
        onClick={this.onClearAllUserButton}>
        {'Clear User List'}
     </Button>
</section>

Function defined:

 private disabledButton= (): boolean => {
    if (this.props.user_list.length == 0) {
      return true
    }
    return false
  }

Is my calling wrong?

disabled prop accepts a boolean value, disabledButton is a function that returns a boolean value. A function is not assignable to a boolean. — Patrick Roberts
– Patrick Roberts, Commented Feb 28, 2020 at 22:49
A function returning a boolean is not assignable to a boolean. Seems logical. Perhaps the function was to be invoked such that the result could be assigned.. — user2864740
– user2864740, Commented Feb 28, 2020 at 22:49

Alex Wayne · Accepted Answer · 2021-07-06 22:34:12Z

47

You're passing a function that returns a boolean (type () => boolean) to a property that expects a boolean (type boolean). You just have to actually execute your function.

disabled={this.disabledButton()}

This error message tells you everything:

"Type '() => boolean' is not assignable to type 'boolean'"

() => boolean is the function you are trying to assign, and boolean is the type it's expecting. It's up to you to notice what those two types are and figure out how to make them match.

edited Jul 6, 2021 at 22:34

answered Feb 28, 2020 at 22:50

Alex Wayne

188k52 gold badges328 silver badges363 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

TypeScript error: Type '() => boolean' is not assignable to type 'boolean'

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related