Playing around with Swift and subscripts

gistfile1.swift

import UIKit

extension Array {
    
    subscript(index:Int,defaultValue def:T) -> T {
            if ( (0 <= index) && (index < self.count) ) {
                return self[index]
            }
            else {
                return def
            }
    }
}

var arr = ["one","two","three"]
let s = arr[4, defaultValue:"test"]
let t = arr[1, defaultValue:"test"]

Here's a tweak that will allow return of Optional nil for invalid indexes, if that's desirable:

extension Array {

    subscript(index:Int, defaultValue def:T?) -> T? {
        if ( (0 <= index) && (index < self.count) ) {
            return self[index]
        }
        else {
            return def
        }
    }
}

var arr = ["one","two","three"]
let s = arr[4, defaultValue:"test"]
let t = arr[1, defaultValue:"test"]
let u = arr[10, defaultValue:nil]

And here's a variation of that last that uses T! so that you can just check if result == nil rather than doing the Optional stuff

import UIKit

extension Array {

    subscript(index:Int, defaultValue def:T!) -> T! {
        if ( (0 <= index) && (index < self.count) ) {
            return self[index]
        }
        else {
            return def
        }
    }
}

var arr = ["one","two","three"]
let s = arr[4, defaultValue:"test"]
let t = arr[1, defaultValue:"test"]
let u = arr[10, defaultValue:nil]