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iosswiftdictionary
A.Alqadomi
A.Alqadomi

Reputation: 1589

Dictionary (key , value) order

Assume i have the following code 

var dictionary = ["cat": 2,"dog":4,"snake":8]; // mutable dictionary
var keys  = dictionary.keys
var values = dictionary.values
for e in keys {
    println(e)
}
for v in values {
    println(v)
}

would the dictionary.keys and dictionary.values have the same order

for example if the dictionary.keys is "dog","snake","cat" would the dictionary.values be always 4,8,2? i tried it on the playground and the result always indicated that they have the same order

Upvotes: 0

Views: 327

Answers (2)

Martin R
Martin R

Reputation: 539745

The definition of the keys and values property is preceded by the following comments:

/// A collection containing just the keys of `self`
///
/// Keys appear in the same order as they occur as the `.0` member
/// of key-value pairs in `self`.  Each key in the result has a
/// unique value.
var keys: LazyBidirectionalCollection<MapCollectionView<[Key : Value], Key>> { get }

/// A collection containing just the values of `self`
///
/// Values appear in the same order as they occur as the `.1` member
/// of key-value pairs in `self`.
var values: LazyBidirectionalCollection<MapCollectionView<[Key : Value], Value>> { get }

My interpretation of

Keys/Values appear in the same order as they occur as the .0/.1 member of key-value pairs in self.

is that dictionary.keys and dictionary.values return the keys and values in "matching" order.

So the key-value pairs of a dictionary do not have a specified order, but the first, second, ... element of dictionary.values is the dictionary value corresponding to the first, second, ... element of dictionary.keys.

Upvotes: 1

Kirsteins
Kirsteins

Reputation: 27335

No, it is not guaranteed to be in the same order. From documentation:

Swift’s Dictionary type is an unordered collection. The order in which keys, values, and key-value pairs are retrieved when iterating over a dictionary is not specified.

Upvotes: 4

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