Create a method that specifies the signature to include a function as a parameter

Question

Create a method that specifies the signature to include a function as a parameter

I am interested in defining a Type Definition that adheres to this function:

var a : MyInterface = function(func : <T>(t: T) => number) {
  console.log("do Nothing");
  return func(123) + " someString";
}

My goal is to create an Interface that accepts a function f that returns a number as a parameter and itself returns a string. From what I understand, the Interface should be structured like this.

interface MyInterface {

    (func: (<T>(t: T) => number)) => string;
}

However, there is an issue with the final '=>' symbol causing it to show an error message ':' expected.

If I remove the return type 'string', the compiler is content. How can I address this problem?

typescript

Answer 1

Answer №1

When working with interfaces, the return type of a callable signature is denoted by using : instead of =>. Therefore, in your specific scenario, the interface would look like this:

interface MyInterface {
    (func: (<T>(t: T) => number)): string;
}

However, if you simply need to declare a function type, it is recommended to use the shorthand syntax which uses =>.

type MyFunction = (func: (<T>(t: T) => number)) => string

The benefit of the former syntax is that it allows for defining overload signatures and hybrid types that are not only callable but also possess properties.

Answer 2

When working with interfaces, the return type of a callable signature is denoted by using : instead of =>. Therefore, in your specific scenario, the interface would look like this:

interface MyInterface {
    (func: (<T>(t: T) => number)): string;
}

However, if you simply need to declare a function type, it is recommended to use the shorthand syntax which uses =>.

type MyFunction = (func: (<T>(t: T) => number)) => string

The benefit of the former syntax is that it allows for defining overload signatures and hybrid types that are not only callable but also possess properties.

Create a method that specifies the signature to include a function as a parameter

Answer №1

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