Скачать или смотреть Fixing the TypeScript Error: Argument of Type '(response) = void' is Not Assignable

Understand and resolve the TypeScript error regarding function argument types in your code. Learn how to ensure type compatibility in your async functions.
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Understanding and Fixing a Common TypeScript Error

TypeScript enhances the JavaScript experience by introducing strong typing, which helps catch errors early in the development process. However, with these benefits can come some frustrations, particularly when it comes to function types. One common issue developers encounter is the error message: "Argument of type '(response: IResponse) = void' is not assignable to parameter of type '(value: void) = void | PromiseLike void '." If you're facing this issue, don't worry—you're not alone. In this post, we'll break down this error, understand its causes, and explore solutions to fix it effectively.

The Problem at Hand

This error typically arises from a mismatch in function type signatures. The core of the problem lies in the expectations of the functions you're working with. In your code, you have a function that takes an argument ((response: IResponse) => void) being used where a function without arguments is expected ((value: void) => void | PromiseLike<void>).

To illustrate the situation, let's look at a simplified example:

[[See Video to Reveal this Text or Code Snippet]]

In this example, caller expects a function that does not take any parameters, but myArg expects one. When trying to execute caller(myArg), an error is thrown because the expected argument type does not match.

Analyzing the Code

In your specific case, you have the following structure:

An asynchronous function getInfoById that is expected to return a Promise<void>.

The check function which invokes getInfoById and uses .then() to handle the response.

Because getInfoById returns Promise<void>, the .then() handling afterwards won't provide any arguments to the callback. This is the root cause of your TypeScript error.

The Solution

To resolve the error, you'll need to adjust the type of the promise returned by your getInfoById function. Specifically, you want it to return a Promise<IResponse> instead of Promise<void>. This modification indicates that your asynchronous function will supply a value of type IResponse to the calling .then() method, which aligns with what your code expects.

Adjusting the Function Type

Here’s how you can modify the getInfoById function:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By ensuring that your function signatures match the required types, you can eliminate the type errors that Typescript raises. Remember, whenever you face assignment or type mismatch errors in TypeScript, it's beneficial to check the expected types of the function parameters and return types carefully. This approach not only helps resolve current issues but also paves the way for writing clearer and more maintainable code.

With this correction applied, you should be able to move past the error and have a more robust solution in place. Happy coding!