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Discussion on: Creating a typed "compose" function in TypeScript

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skurfuerst profile image
Sebastian Kurfürst

Hey Matt,

Thanks for your article!

I am having a question I don't really understand: In my understanding, the compose function can compose functions which return different types than what they expect; i.e. when plugging the pipe together, the output type of the first function must match the input type of the second function.

So, as I understand it, if you compose n functions together, you would have n+1 types.

Is this also handled by your function above? If so, I do not understand yet how this works :)

All the best,
Sebastian

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ascorbic profile image
Matt Kane Author

Hi Sebastian,
This isn't as smart as that: it expects that they all return the same type. If be interested to see if there's a way of typing the other sort though.

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skurfuerst profile image
Sebastian Kurfürst

Hey Matt,

the only way I see it is via N+1 different generic types - though that is ofc. not as nice as your generic implementation.

See:

All the best, Sebastian

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stereobooster profile image
stereobooster

There is a way to simulate it, but wiht limitations github.com/reduxjs/redux/blob/686d...

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ascorbic profile image
Matt Kane Author

Yeah, I can't see any way that doesn't boil down to "use lots of repetitive overloads"