[swift-evolution] map-like operation that returns a dictionary

[Craig Cruden]

There is no equivalent to something like 

array.zipWithIndex.toMap (or in this case array.zipWithIndex.toDictionary // where zipWithIndex creates tuples with the index - a specialized case of zip for Arrays with indexes.



> On 2016-01-11, at 2:41:59, Ross O'Brien via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Or an enumeration followed by a forEach.
> ["John", "Mike", "Amy", Kavin"].enumerate().forEach {
>     dic[$0] = $1
> }
> That said, it requires creating a dictionary var first, not a let. If there was an initialiser for Dictionary which took an Array or EnumerateSequence, that might be useful. I'm not sure how I'd attempt to write such an initialiser though.
> 
> 
> On Sun, Jan 10, 2016 at 7:08 PM, Donnacha Oisín Kidney <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> I think that use of map is generally discouraged. forEach would probably be more explicit, or a for-loop.
> 
>> On 10 Jan 2016, at 18:58, 肇鑫 via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> You can use dictionary in a map. You just ignore the return value of the map.
>> 
>> var dic = [Int:String]()
>> var index = 0
>> 
>> ["John", "Mike", "Amy", "Kavin"].map {
>>     dic.updateValue($0, forKey: index)
>>     index += 1
>> }
>> 
>> print(dic) // [2: "Amy", 0: "John", 1: "Mike", 3: "Kavin"]
>> 
>> zhaoxin
>> 
>> On Mon, Jan 11, 2016 at 1:50 AM, Kenny Leung via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> Hi All.
>> 
>> I find that instead of using map() on arrays, I more often use an operation that returns a dictionary from an array. A common case is fetching an array of data, then creating a local cache of it indexed by ID.
>> 
>> Is there a name for this operation? Is this something that others would like to see added to the standard library?
>> 
>> -Kenny
>> 
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>> 
>> 
>> -- 
>> 
>> Owen Zhao
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> 
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