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

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].

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]