Incorrect example code in Readme about promise

[khanlou]

It isn't clear from the readme, but it's an extension I added onto URLSession that sends the request and returns a promise. It works almost exactly the same as the promise above it in the readme. What do you propose for fixing the lack of clarity?

[SintraWorks]

That explains it. I had a feeling you did not simply make a mistake, but I couldn't add things up...

Anyway, for making it clear what is going on, you could mention that you're using the extension just before the first code example that uses it. (If your extension is on GitHub, maybe add a link to it.)

And while I'm at it: many thanks for your excellent blog posts!

[SintraWorks]

I made it an excercise to recreate your URLSession extension. Any comments on the result?

extension URLSession {
    open func dataTask(with request: URLRequest) -> Promise<(Data, HTTPURLResponse)> {
        return Promise<(Data, HTTPURLResponse)>(work: { fulfill, reject in
           self.dataTask(with: request, completionHandler: { data, response, error in
                if let error = error {
                    reject(error)
                } else if let data = data, let response = response as? HTTPURLResponse {
                    fulfill((data, response))
                } else {
                    fatalError("Something has gone horribly wrong.")
                }
            }).resume()
        })
    }
}

[khanlou]

Nailed it! The only thing I would change is returning the promise directly instead of creating an intermediate variable and returning that.

[SintraWorks]

Thanks, getting rid of the intermediate makes sense, of course.

As an update on "fixing the lack of clarity": you could show the extension in the Creating Promises paragraph, right where you show how to wrap URLSession. Rather than assigning the promise to a variable, show the extension code. You wouldn't even need to adjust the the paragraph text around it, since the extension code exemplifies the idea of "wrapping" an API even more clearly than the current example.

[kelan]

@SintraWorks: Minor correction in that code listing:
I think you should use self instead of URLSession.shared in this line:

            URLSession.shared.dataTask(with: request, completionHandler: { data, response, error in

so that you make a task in the session that receives the method call, instead of always in the shared session.

[SintraWorks]

@kelan: Thanks for noticing that. You are right, of course.