How to convert String to Int in Swift?

Question

There has been same titles of this question but different situations. In this case this is very simple but I can't find a same problem online. So here's the code

class ViewController: UIViewController {

@IBOutlet weak var fldTotalUnits: UITextField!

var intTotalUnits:Int? = Int(fldTotalUnits)

The error here says "Cannot use instance member 'fldTotalUnits' within property initializer;..." I tried replacing var with let, I tried NSString, I tried .toInt() but nothign worked... so how do I this?

1. put that `Int` creation code into some `func` 2. use the `text` property of the textfield instead. — luk2302, Mar 21 '17 at 13:37
There are [plenty of existing questions/answers](http://stackoverflow.com/search?q=%5Bswift%5D+Cannot+use+instance+member+within+property+initializer) on that error. — rmaddy, Mar 21 '17 at 13:55
Possible duplicate of [How to initialize properties that depend on each other](http://stackoverflow.com/questions/25854300/how-to-initialize-properties-that-depend-on-each-other) — rmaddy, Mar 21 '17 at 13:56

score 1 · Accepted Answer · answered Mar 21 '17 at 13:56

1

String to Int conversion is not complicated. You simply do the conversion at the wrong place. You are trying to reference one member in the initialization of another member, that is not allowed. In this particular case simply because fldTotalUnits has the value nil when you would try to use it via Int(fldTotalUnits). When creating an instance of your class ViewController fldTotalUnits is set to nil and initialized with a useful value later. Therefore what you have to do in the first place is move the line into a separate method:

func doSomething() {
    var intTotalUnits:Int? = Int(fldTotalUnits)
}

Now you will see that the compiler complains about there not being a suitable initializer because you have to access the text property of fldTotalUnits instead of using the actual textfield:

func doSomething() {
    var intTotalUnits:Int? = Int(fldTotalUnits.text!)
}

Now you can think about moving the declaration of intTotalUnits to somewhere else, but setting its value has to happen in some method.

answered Mar 21 '17 at 13:56

luk2302

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you're actually right! i have to put the conversion inside a function and add that .text! OH MY GOOOOOD! You just solved my problem that's giving me pain for hours.. I LOVE YOU MAN THANK YOU FOR BEING ALIVE!!! – Geni-sama Mar 21 '17 at 13:57
`var intTotalUnits: Int { return Int(fldTotalUnits.text!) ?? 0}` – Leo Dabus Mar 21 '17 at 13:58
1

@LeoDabus yeah, sure. There was already an answer for that which somehow got downvotes and was deleted - I wanted to explain what went wrong here since OP got confused in the first place. – luk2302 Mar 21 '17 at 13:59
if i may ask, are those variables declared inside the function accessible throughout the program? – Geni-sama Mar 21 '17 at 14:01
variables declared inside the function are accessible only inside the function – Leo Dabus Mar 21 '17 at 14:02
@Geni-sama that is why I wrote the last sentence, you might consider using Leo's comment instead anyway since it probably does *exactly* what you want. – luk2302 Mar 21 '17 at 14:03
i tried the code, it's running, however, there's a warning that says "initialization of variable 'intTotalUnits' was never used; consider replacing..." is this okay? should i just ignore this? – Geni-sama Mar 21 '17 at 14:05
add a `print(intTotalUnits)` inside viewDIdLoad or use it in another method – Leo Dabus Mar 21 '17 at 14:07

Ashley Mills · Answer 2 · 2017-03-21T13:49:37.267

0

The code in your question is trying to create an Int from a UITextField, not a String. What you should say is something like…

var intTotalUnits:Int?


func updateTotalUnits()
    guard let text = fldTotalUnits.text else { return }

    intTotalUnits = Int(text)    
}

edited Mar 21 '17 at 13:49

answered Mar 21 '17 at 13:44

Ashley Mills

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But if OP replaces his statement with your code it would still not compile, he has to additionally put it in a separate function. – luk2302 Mar 21 '17 at 13:46
Well, I hope the OP doesn't just copy my code without thinking about it! – Ashley Mills Mar 21 '17 at 13:46
it says consecutive delcarations on a line must be separated by ';' (semi colon) and another error that says "expected declaration" – Geni-sama Mar 21 '17 at 13:47
Oh, I guess he did! – Ashley Mills Mar 21 '17 at 13:48
Tadaaa :D clearly OP does not know where to put that code. The compiler message does not complain about the `text` for a reason, its first concern is the actual location of the snippet. – luk2302 Mar 21 '17 at 13:49
@luk2302 we are answering to this question not to something else. We do not have to know if he knows where to put code if he didn't ask for it. – Tarvo Mäesepp Mar 21 '17 at 13:50
why is it so complicated for swift for just string to int conversion? :'-( – Geni-sama Mar 21 '17 at 13:51
`String` to `Int` conversion is very simple. What you were trying to do was `UITextField` to `Int` conversion… – Ashley Mills Mar 21 '17 at 15:58

How to convert String to Int in Swift?

2 Answers2