Specify the return type of an arrow function in an interface declaration-CodePudding

I want to tell typescript that I'll be using an interface that offers a function named "foo" that always returns a string. The body of the function will be defined by the object implementing the interface.

Something like this :

export interface IMyInterface {
   foo: ():string => void;
}

Unfortunately the compiler says that this :string shouldn't be there. What's the correct syntax? If I remove :string then the function returns type "any" and I don't want to allow that.

CodePudding user response：

The value on the RHS of the arrow is the return type. You're currently saying it is void.

You can also use the alternative syntax (bar below) where the "is a function" status is declared in the name.

interface Example {
    foo: () => string;
    bar(): string;
}

CodePudding user response：

The type of the arrow function comes after =>.

export interface IMyInterface {
   foo: () => string;
}

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