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Discussion on: Type | Treat Challenge 2

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johnnhoj profile image
John Cheng •

In the advanced/intermediate challenge. It states that 'Bobby Tables' cannot have peanuts but to me, the solution seems to do the opposite and actually keep all the candies where there are peanuts 🤔

type HasPeanuts<A> = A extends { peanuts: true } ? A : never;
type AllCandiesWithoutPeanuts = HasPeanuts<AllCandies>
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dungdung profile image
Houston • 
type AllCandies = Extract<ResultsFromHalloween, {candy: true}>;
type AllTricks = Extract<ResultsFromHalloween, {trick: true}>;
type AllCandiesWithoutPeanuts = Exclude<AllCandies, {peanuts: true}>;
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johnnhoj profile image
John Cheng • • Edited

I agree with your implementation. I was discussing the solution provided in this post :)
Maybe @gcrev93 can help me if I misinterpreted it

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dungdung profile image
Houston •

My bad, should have said something instead of just plopping down a solution - yes you are correct saying that:

type AllCandiesWithoutPeanuts = HasPeanuts<AllCandies>
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is the opposite of the solution. Something more correct would have the inverted type. I'm not sure how one would go from HasPeanuts to something like OmitsPeanuts but declaring it from scratch is straightforward:

type OmitsPeanuts<A> = A extends { peanuts: true } ? never : A;
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ricklove profile image
Rick Love •

Bobby is on his way to the hospital now. Thankfully somebody had an epi-pen ready.

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mattiasbuelens profile image
Mattias Buelens •

Also, the proposed solution for AllCandies removes all candies from the union, instead of only keeping the candies.

type AllCandies = Exclude<ResultsFromHalloween, {candy: true}>
// type AllCandies = Toothpaste | Pencil
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This should probably use Extract instead of Exclude:

type AllCandies = Extract<ResultsFromHalloween, {candy: true}>
// type AllCandies = SnackBars | Gumballs | Apples | SnickersBar | Cookies
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