CODEWITHSUNDEEP
iosxcodeswiftnsstring
rocket101
rocket101

Reputation: 7537

How do I convert an NSString to an integer using Swift?

I need to convert an NSString to an integer in Swift: Here's the current code I'm using; it doesn't work: 

 var variable = (NSString(data:data, encoding:NSUTF8StringEncoding))
 exampeStruct.otherVariable = (variable).intValue

Variable is a normal varable, and exampleStruct is a struct elsewhere in the code with a subvariable otherVariable.

I expect it to set exampleStruct.otherVariable to an int value of the NSString, but I get the following error: 

"Cannot convert the expression's type () to type Float"

How do I convert an NSString to int in Swift?

Upvotes: 11

Views: 9288

Answers (3)

Leo Dabus
Leo Dabus

Reputation: 236528

edit/update:

No need to use NSString when coding with Swift. You can use Swift native String(data:) initializer and then convert the string to Int:

if let variable = String(data: data, encoding: .utf8),
    let integer = Int(variable) {
    exampeStruct.otherVariable = integer
}

If other variable is a Float type:

if let variable = String(data: data, encoding: .utf8),
    let integer = Float(variable) {
    exampeStruct.otherVariable = integer
}

Upvotes: 0

surui
surui

Reputation: 1542

I know you already got your answer, but I just want to explain what (I think) might not be trivial

First, we have some NSData we want to convert to NSString, because no one guaranties the data is a valid UTF8 buffer, it return an optional 

 var variable = NSString(data:data, encoding:NSUTF8StringEncoding)

Which means variable: NSString?

Usually NSString is bridged to swift's String, but in this case, we use an NSString constructor - you can think about it more as a "Foundation"-like syntax that wasn't directly imported to swift (as there's no bridge for NSData)

we can still use the 'Foundation' way with NSString

if let unwrappedVariable = variable {
    var number = unwrappedVariable.intValue
}

if number is a Float, but the string is a string representation of an integer

if let unwrappedVariable = variable {
    var number: Float = Float(unwrappedVariable.intValue)
}

if both number and the string (representation of) are floats:

if let unwrappedVariable = variable {
    var number:Float = unwrappedVariable.floatValue
}

Anyway, there's a small problem with using Foundation. For these types of conversions it has no concept of an optional value (for int, float). It will return 0 if it cannot parse a string as and integer or float. That's why it's better to use swift native String:

if let variable: String = NSString(data: data, encoding: NSUTF8StringEncoding) {
    if let integer = variable.toInt() {
        var integerNumber = integer
        var floatNumber = Float(integer)
    }
}

Upvotes: 1

MahatmaManic
MahatmaManic

Reputation: 953

It looks to me like the problem might not be the Int conversion, but rather that the exampleStruct is expecting a Float.

If that's not the issue however (and granted, Xcode errors for Swift often seem to be more about the line number rather than about the actual problem) then something like this should work for you?

var ns:NSString = "1234"
if let i = (ns as String).toInt() {
    exampleStruct.otherVariable = i
}

Upvotes: 1

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