swift get values from array and put them into another array using recursion function

Question

I want to get values from one array, and put them into another array using recursion function.And want to notice that I do not want to use loop(like 'for in loop')

var rudics = ["one", "two", "three", "four", "five", "six"]
var array = [""]
func changeArray (var new:[String]) {
    array = [new.first!]
    if new.count > 0 {
    new.removeLast()
    changeArray(new)
    }
}

changeArray(rudics)

it gives me an error

fatal error: unexpectedly found nil while unwrapping an Optional value
Playground execution failed: Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0).

and so on..

please help me!

the error might be at array = [new.first!]. You are doing it before checking for new.count and new might be empty at that time. — saurabh
– saurabh, Commented May 29, 2015 at 7:43

Matteo Piombo · Accepted Answer · 2015-05-29 07:47:15Z

3

You might consider something like this:

var rudics = ["one", "two", "three", "four", "five", "six"]
var array = [String]()
func changeArray (var new:[String]) {
    if let first = new.first {
        array.append(first)
        new.removeAtIndex(0)
        changeArray(new)
    }
}

changeArray(rudics)

edited May 29, 2015 at 7:47

answered May 29, 2015 at 7:41

Matteo Piombo

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8 Comments

alphonse Over a year ago

when I call 'array' it gives [one", "one", "one", "one", "one", "one"]

Matteo Piombo Over a year ago

Yep ... edited it. It was due to the fact that in your first example you take the first item but remove the last

Matteo Piombo Over a year ago

You might consider correcting it in your question, since it was not central to the problem you posted.

alphonse Over a year ago

Just it confused because I tried to reverse this array last time :) .At first I wrote new.removeAtIndex(0) as you did . :)

alphonse Over a year ago

If I want to use optional value like new.first, should I always use optional binding? not just if statement?thats why my code shows an error?

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