Get the value of a Swift variable from a constructed name

Question

I am stuck at a problem which i am trying to figure out in Swift 4.

Let say, i have the below variables

let var1 = "One"
let var2 = "Two"
let var3 = "Three"

var counter = 1

// Loop Start

let currentVariable = "var" + "\(counter)"

//Fetch the value of variable stored under currentVariable

counter += 1

//Loop end

I am trying to get the value based on variable name stored under currentVariable.

Use of array is one solutions but I am trying to fetch this in case I have random numbers and not in a specific order. — Tapas Kumar Pradhan, Aug 28 '17 at 21:37
Possible duplicate of [Create a variable in swift with dynamic name](https://stackoverflow.com/questions/27716931/create-a-variable-in-swift-with-dynamic-name) — jscs, Aug 28 '17 at 21:44
This [is an antipattern](https://stackoverflow.com/questions/6049175/is-it-possible-to-reference-a-variable-with-a-string-and-an-int). — jscs, Aug 28 '17 at 21:47

score 1 · Accepted Answer · answered Aug 28 '17 at 22:00

1

You can set up dictionary, replacing your variable names with keys.

let letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
var myDictionary:[String:String] = ["var1":"One", "var2":"Two", "varA":"A", "varB":"B"]  // note, both sides can be different types than String

for x in 0...9 {
    let myKey = "var" + String(x)
    printValue(myKey)
}
for x in letters.characters {
    let myKey = "var" + String(x)
    printValue(myKey)
}

The simple function:

func printValue(_ key:String) {
    let myValue = myDictionary[key]
    if myValue != nil {
        print(myValue)
    }
}

I'm pretty sure you can make things a bit more elegant, but you get the idea. Also, keep in mind that a Dictionary is "unordered", as opposed to an array.

answered Aug 28 '17 at 22:00

Yes. this seems more like the solution. I will understand it more and implement in on my problem. Thanks again. – Tapas Kumar Pradhan Aug 28 '17 at 22:14
1

I'd like to add that it's better to use dictionary, map, hashtable, etc than trying to dynamically access variables by string name in pretty much all cases but not just in swift, also in php and others. Why? Security and structure. – HumbleWebDev Aug 29 '17 at 00:55
I never thought about that. I come from a, um, Assembler/COBOL start in the early 1980s and *forget* that side of things. Great addition! – Aug 29 '17 at 01:01

score 0 · Answer 2 · answered Aug 28 '17 at 21:39

0

Use an array

let myArray = ["one", "two", "three"];
var counter = 1;
print(myArray[counter]);

answered Aug 28 '17 at 21:39

HumbleWebDev

555
4
20

Thanks. Is there a way without Array? I main intentions was to see how can i get the value from a derivative variable name – Tapas Kumar Pradhan Aug 28 '17 at 21:44
You wouldn't want to do that anyways. If swift has such an operation it would be slower/less secure. This is the same reason we avoid variable variables in PHP. – HumbleWebDev Aug 28 '17 at 21:45
If you want to use named element access, I encourage you to use whatever Swift's map class is. – HumbleWebDev Aug 28 '17 at 21:47
1

Thanks @TheUnholyProgrammer , i will try to implement this using array. – Tapas Kumar Pradhan Aug 28 '17 at 21:59
@TapasKumarPradan if you want named access, look up swift dictionaries. – HumbleWebDev Aug 28 '17 at 22:00
1

Yep dictionary seems to be a better solution. – Tapas Kumar Pradhan Aug 28 '17 at 22:13

Get the value of a Swift variable from a constructed name

2 Answers2