Can't change String Array in Swift 2 after returning it from function

Question

I have this playground example:

import UIKit

var testArray: [[String]] = [["2","2"],["1","1"]]

testArray[0][0] = "3" // Working

func getTestArray() -> [String] {

    return testArray[0]

}

var test = getTestArray()[0] = "4" // Error: Immutable Value

How can i get the reference of testArray to change it

Changing test won't change testArray!

Swift arrays are *value types.* Your function returns a *value,* not a reference to the original array. — Martin R, Feb 13 '18 at 09:43
https://stackoverflow.com/questions/27364117/is-swift-pass-by-value-or-pass-by-reference — Anik Islam Abhi, Feb 13 '18 at 09:49
@Sweeper it's for a project that uses an outdated sdk and sadly can't be updated — Jonas, Feb 13 '18 at 10:14

score 3 · Accepted Answer · answered Feb 13 '18 at 09:47

3

getTestArray() returns a value, not a reference. Therefore, the value returned by a function cannot be edited, only variables can be changed. To change the variable, use:

var testVal = getTestArray() // get the value
testVal[0] = "4" // change the value
testArray[0] = testVal // SET the value of the reference `testArray` (change the value)

answered Feb 13 '18 at 09:47

Papershine

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With this solution getTestArray() would be useless. You could get testArray directly. But maybe there is no better solution – Jonas Feb 13 '18 at 10:15
@JonasSchafft To be honest, why you need such a function? – Papershine Feb 13 '18 at 10:18
Difficult to explain. But it would help me in an specific situation. – Jonas Feb 13 '18 at 10:49

score 0 · Answer 2 · answered Feb 13 '18 at 09:41

0

You need to assign value to test and than change it:

var test = getTestArray()
test[0] = "4"

answered Feb 13 '18 at 09:41

Ilya Kharabet

4,203
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Then i`m not changing testArray – Jonas Feb 13 '18 at 09:41

score 0 · Answer 3 · answered Feb 13 '18 at 09:43

0

var test = getTestArray()
test[0] = "4"
print(test)

answered Feb 13 '18 at 09:43

Catherine

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15

Then i`m not changing testArray – Jonas Feb 13 '18 at 09:44
I need to change testArray. Not something else. Can i get the reference? – Jonas Feb 13 '18 at 09:45
They are not reference types – Catherine Feb 13 '18 at 09:46
use classes instead – Catherine Feb 13 '18 at 09:49

Can't change String Array in Swift 2 after returning it from function

3 Answers3