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toMap should take a mapping function #600

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Daniel15 opened this issue Aug 25, 2015 · 4 comments
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toMap should take a mapping function #600

Daniel15 opened this issue Aug 25, 2015 · 4 comments

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@Daniel15
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It would be nice if toMap accepted a mapping function to specify what the values should be:

var input = Immutable.List(['a', 's', 'd', 'f']);
var output = input.toMap(x => x.toUpperCase() + '!'); 
// output = Map { 'a': 'A!', 's': 'S!', 'd': 'D!', 'f': 'F!' }

You could do input.toMap().map(x => x.toUpperCase() + '!') at the moment but it's not as nice 😜

.NET LINQ has similar functionality, except it uses the function to specify the key rather than the value: https://msdn.microsoft.com/en-us/library/bb549277(v=vs.95).aspx
@ddaza
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ddaza commented Aug 25, 2015

The current functionality is done by design, per the documentation of toMap():

Note: This is equivalent to Map(this.toKeyedSeq()), but provided for convenience and to allow for chained expressions.

So the chaining that you're doing is exactly how they meant it to work, I think 😄.

@ChrisMarinos
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Note, the code you have would actually produce:

"Map { 0: "A!", 1: "S!", 2: "D!", 3: "F!" }" instead of Map { 'a': 'A!', 's': 'S!', 'd': 'D!', 'f': 'F!' }

I'd like a value selector as mentioned above, but I'd actually much prefer a key selector. I find that the lack of a key selector is a much more significant limitation.

@dubrowgn dubrowgn mentioned this issue Feb 15, 2016
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@dubrowgn
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I posted some code for this on #697. Thoughts?

This was referenced Feb 15, 2016
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@leebyron
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leebyron commented Mar 8, 2017

Closing this aging issue.

Trying to shy away from toMap and family, I'd prefer not to complicate them further.

@leebyron leebyron closed this as completed Mar 8, 2017
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5 participants
@leebyron @Daniel15 @ChrisMarinos @ddaza @dubrowgn