DictionarySorting

What

DictionarySorting is a Swift Package Manager package for iOS/tvOS (10.0 and above), watchOS (4.0 and above), and macOS (10.14 and above), under Swift 5.0 and above, implementing an extension to Dictionary that provides an easy-to-use and ergonomic "swifty" way to sort a dictionary, as easy as:

letdata= /* ... */ // a dictionary of some kind
let sorted = data.sorted(by:.keys(.ascending)) // returns an array of the elements stored in the
// dictionary, sorted in ascending order of their keys

The package provides several such sorted(by:) functions, depending on whether one or both the dictionary's Key and Value types conform to Comparable:

extensionDictionarywhere Key:Comparable{publictypealiasKeyOrder=SortOrderpublicenumKeySorter{case keys(KeyOrder)}publicfunc sorted(by sorter:KeySorter)->[Element]}extension Dictionary where Value:Comparable{
public typealiasValueOrder=SortOrder
public enumValueSorter{case values(ValueOrder)}
/// Keys will not be in a well-defined order.
public func sorted(by sorter:ValueSorter)->[Element]}extensionDictionarywhere Key:Comparable, Value:Comparable{publicenumKeyValueSorter{case keysOnly(KeyOrder)case valuesOnly(ValueOrder) // Keys will not be in a well-defined order.
case valuesThenKeys(values:ValueOrder, keys:KeyOrder)}publicfunc sorted(by sorter:KeyValueSorter)->[Element]}

Note that sorting by values without also sorting by keys does not guarantee a stable order for the keys. For example,

letdata=[5:70,6:70,7:60,8:50]letvalueSortedData= data.sorted(by:.valuesOnly(.ascending))

may result in either of these arrays:

[(key:8, value:50),(key:7, value:60),(key:5, value:70),(key:6, value:70),]

and

[(key:8, value:50),(key:7, value:60),(key:6, value:70),(key:5, value:70),]

The same is true with

letdata=[5:70,6:70,7:60,8:50]letvalueSortedData= data.sorted(by:.values(.ascending))

Note also that there's no option

case keysThenValues(keys: KeyOrder, values: ValueOrder)

in the KeyValueSorter enumeration

publicenumKeyValueSorter{case keysOnly(KeyOrder)case valuesOnly(ValueOrder) // Keys will not be in a well-defined order.
case valuesThenKeys(values:ValueOrder, keys:KeyOrder)}

because the keys in a dictionary are guaranteed to be unique and, therefore, once the dictionary is sorted by its keys, its values will be fixed and their order can no longer change.

The package also provides some useful global functions:

publicfunc sort<K:Hashable&Comparable, V>(_ subseq:Dictionary<K,V>.SubSequence,
_ sorter:Dictionary<K,V>.KeySorter)->[Dictionary<K,V>.Element]
public func sort<K: Hashable &Comparable, V>(_ kvPairs:[Dictionary<K,V>.Element],
_ sorter:Dictionary<K,V>.KeySorter)->[Dictionary<K,V>.Element]
public func sort<K: Hashable, V: Comparable>(_ subseq:Dictionary<K,V>.SubSequence,
_ sorter:Dictionary<K,V>.ValueSorter)->[Dictionary<K,V>.Element]
public func sort<K: Hashable, V: Comparable>(_ kvPairs:[Dictionary<K,V>.Element],
_ sorter:Dictionary<K,V>.ValueSorter)->[Dictionary<K,V>.Element]
public func sort<K: Hashable &Comparable, V: Comparable>(_ subseq:Dictionary<K,V>.SubSequence,
_ sorter:Dictionary<K,V>.KeyValueSorter)->[Dictionary<K,V>.Element]
public func sort<K: Hashable &Comparable, V: Comparable>(_ kvPairs:[Dictionary<K,V>.Element],
_ sorter:Dictionary<K,V>.KeyValueSorter)->[Dictionary<K,V>.Element]

Dependencies

DictionarySorting depends on two other libraries of mine, SortOrder and DictionarySlicing.

Installation

DictionarySorting is provided only as a Swift Package Manager package, because I'm moving away from CocoaPods and Carthage, and can be easily installed directly from Xcode.

License

DictionarySorting is available under the MIT license. See the LICENSE file for more info.