How to set the Type of a function in Typescript, when passing that into another function?

Question

Here is my function:

const payout = (asset: ILPAsset, type: string)
    => type === 'daily' ? asset.lastPayout : asset.historical;

And where I'm using it:

@bind
private mapDailyAssets(payoutType: string, payout: payoutFunc, assets: ILPAsset[], currency: string) {
  return assets.map((asset) => (
    <div className={b('table-row')()} key={asset.symbol}>
      <div>{asset.symbol}</div>
      <div className={b('asset-value')()}>{formatMoney(payout(asset, payoutType), currency)}</div>
    </div>
  ));
}

I'm getting errors when trying to set an interface for type payoutFunc:

interface payoutFunc: (asset: ILPAsset, type: string) => string;

But also getting this error:

invoke an expression whose type lacks a call signature

Aaron Beall · Accepted Answer · 2018-09-25 14:10:22Z

1

Your syntax for declaring a function signature interface is not quite right. It should look like this:

interface payoutFunc { 
  (asset: ILPAsset, type: string): string;
}

Or you could use a type alias:

type payoutFunc = (asset: ILPAsset, type: string) => string;

In either case you can use this type as a prop somewhere else:

interface MyProps {
  foo: string;
  bar: number;
  payout: payoutFunc;
}

answered Sep 25, 2018 at 14:10

Aaron Beall

52.6k26 gold badges91 silver badges109 bronze badges

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

1 Comment

Leon Gaban Over a year ago

Thank you! This was exactly what I needed, other questions on stack just covered the function itself, wasn't looking for the Typescript function type syntax.

Collectives™ on Stack Overflow

How to set the Type of a function in Typescript, when passing that into another function?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related