Type 'void' is not assignable to type '((err: any) => void)

Question

I have the following interface in typescript

interface ConfigOptions {
    autoloadCallback: (err: any) => void;
}

in my implementation I have

options = {
  autoloadCallback: this.autoLoadCallBack(err)
}

public autoLoadCallBack(err: any) : void {
  console.log('im a callback');
};

which throws the following error

Types of property 'autoloadCallback' are incompatible. Type 'void' is not assignable to type '((err: any) => void) | undefined'.

since autoLoadCallBack takes any type and doesn't return anything should it match the interface specification?

options.autoloadCallback is supposed to be a function, right? But you've set it to the void return value of a function. And the error is telling you that. Why not options = {autoloadCallback: this.autoLoadCallback.bind(this)} or something? — jcalz
– jcalz, Commented Oct 23, 2018 at 15:46

Joe Clay · Accepted Answer · 2018-10-23 15:46:28Z

2

You are calling this.autoLoadCallBack then assigning the return value of that function (which in this case is nothing, as it's void) to options.autoloadCallback.

You seem to be trying to assigning the this.autoLoadCallBack function to options.autoloadCallback directly, which would look like this:

options = {
  autoloadCallback: this.autoLoadCallBack
}

public autoLoadCallBack(err: any) : void {
  console.log('im a callback');
};

answered Oct 23, 2018 at 15:46

Joe Clay

36.1k6 gold badges94 silver badges90 bronze badges

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

2 Comments

user618509 Over a year ago

so why does adding parameters to this.autoLoadCallBack cause this to fail?

Joe Clay Over a year ago

@user618509: this.autoLoadCallBack(err) calls the function, this.autoLoadCallBack is the function. If you want a more practical example, examine the difference between running console.log and console.log("hello, world") in your browser's console.

Collectives™ on Stack Overflow

Type 'void' is not assignable to type '((err: any) => void)

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related