Swift Dictionary: Get values as array

arrays dictionary swift
Stuart picture Stuart · Nov 18, 2014 · Viewed 87.5k times · Source

I have a dictionary containing UIColor objects hashed by an enum value, ColorScheme:

var colorsForColorScheme: [ColorScheme : UIColor] = ...

I would like to be able to extract an array of all the colors (the values) contained by this dictionary. I thought I could use the values property, as is used when iterating over dictionary values (for value in dictionary.values {...}), but this returns an error:

let colors: [UIColor] = colorsForColorSchemes.values
                        ~~~~~~~~~~~~~~~~~~~~~^~~~~~~
'LazyBidrectionalCollection<MapCollectionView<Dictionary<ColorScheme, UIColor>, UIColor>>' is not convertible to 'UIColor'

It seems that rather than returning an Array of values, the values method returns a more abstract collection type. Is there a way to get an Array containing the dictionary's values without extracting them in a for-in loop?

Answer

Stuart picture Stuart · Nov 18, 2014

As of Swift 2.0, Dictionary’s values property now returns a LazyMapCollection instead of a LazyBidirectionalCollection. The Array type knows how to initialise itself using this abstract collection type:

let colors = Array(colorsForColorSchemes.values)

Swift's type inference already knows that these values are UIColor objects, so no type casting is required, which is nice!

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