How to rearrange item of an array to new position in Swift?

Question

Consider the array [1,2,3,4]. How can I rearrange the array item to new position.

For example:

put 3 into position 4 [1,2,4,3]

put 4 in to position 1 [4,1,2,3]

put 2 into position 3 [1,3,2,4].

Answer 1

Swift 3.0+:

let element = arr.remove(at: 3) arr.insert(element, at: 2) 

and in function form:

func rearrange<T>(array: Array<T>, fromIndex: Int, toIndex: Int) -> Array<T>{     var arr = array     let element = arr.remove(at: fromIndex)     arr.insert(element, at: toIndex)      return arr } 

Swift 2.0:

This puts 3 into position 4.

let element = arr.removeAtIndex(3) arr.insert(element, atIndex: 2) 

You can even make a general function:

func rearrange<T>(array: Array<T>, fromIndex: Int, toIndex: Int) -> Array<T>{     var arr = array     let element = arr.removeAtIndex(fromIndex)     arr.insert(element, atIndex: toIndex)      return arr } 

The var arr is needed here, because you can't mutate the input parameter without specifying it to be in-out. In our case however we get a pure functions with no side effects, which is a lot easier to reason with, in my opinion. You could then call it like this:

let arr = [1,2,3,4] rearrange(arr, fromIndex: 2, toIndex: 0) //[3,1,2,4]