Swift Array var issue

Question

    var dictionary = ["1": ["One","Two","Three"],
                      "2": ["A","B","C"]
                     ]

    var array = dictionary ["1"]
    array!.append("Four")

    print("array Count: \(array!.count) array In DictionaryCount: \(dictionary ["1"]!.count)")
    //array Count: 4 array In Dictionary Count: 3

var array has append "Four",but in dictionary it does't, how to append an element in dictionary?

yes as said by @ozgur direct append will not work. you can do that or just reassign the array to dictionary["1"] = array — Ajit Balachandran
– Ajit Balachandran, Commented Oct 25, 2016 at 7:50

Ozgur Vatansever · Accepted Answer · 2016-11-15 09:49:16Z

2

In Swift, arrays are implemented as structs and they are always copied when they are passed around in your code, and do not use reference counting. That being said, array becomes the copy of dictionary[1] in your example so updating the contents of that doesn't affect the original dictionary.

What you should do instead:

dictionary["1"]?.append("Four")

edited Nov 15, 2016 at 9:49

answered Oct 25, 2016 at 7:46

Ozgur Vatansever

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alexburtnik · Accepted Answer · 2016-10-25 07:46:46Z

0

Unlike Objective-C, collections in Swift are not reference types. It means that arrays, dictionaries, strings and almost everything behave like primitives in C/Objective-C (except objects, which are instances of classes, not structures or enums)

You can find more details in this official Apple page: Value and Reference Types

answered Oct 25, 2016 at 7:46

alexburtnik

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