Implement flatMapValues method #1348
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| * Similar to mapValues, but works like flatMap, returning a collection of outputs | ||
| * for each value input. | ||
| */ | ||
| def flatMapValues[V](fn: T => GenTraversableOnce[V]): This[K, V] = |
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we generally use TraversableOnce[V] here, can we stick to that style?
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can you add the same method to def flatMapValues[K, V1, V2](fn: V1 => TraversableOnce[V2])(implicit ev: T <:< (K, V1)): TypedPipe[(K, V2)] =
raiseTo[K, V1].flatMap { case (k, v1) => fn(v1).map { v2 => k -> v2 } } |
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Thanks for adding this. You're right, it comes up, and summingbird added it a long time ago. |
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@johnynek Added the method to TypedPipe, but there appear to be no tests for it. It type checks though :) EDIT: didn't see you provided an example - let me modify |
| @@ -300,6 +302,10 @@ trait TypedPipe[+T] extends Serializable { | |||
| def mapValues[K, V, U](f: V => U)(implicit ev: T <:< (K, V)): TypedPipe[(K, U)] = | |||
| raiseTo[(K, V)].map { case (k, v) => (k, f(v)) } | |||
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| /** Similar to mapValues, but allows to return a collection of outputs for each input value */ | |||
| def flatMapValues[K, V, U](f: V => TraversableOnce[U])(implicit ev: T <:< (K, V)): TypedPipe[(K, TraversableOnce[U])] = | |||
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I think we want TypedPipe[(K, U)] to be the return type. In other words, you have another copy of mapValues here, which you can use if you don't want the flattening, but I think this one should behave exactly as it does on KeyedListLike.
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But if I use fn(v1).map { v2 => k -> v2 } This returns a Traversable[U] (or Traversable[V2] from example above)
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look at my code. It had a flatMap yours does not have.
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😵 Of course, fixed
Implement flatMapValues method
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Thanks! This is useful. |
Sometimes its useful to have flatMapValues, similar to mapValues, but flatter.