Convert String to CGFloat in Swift

I'm new to Swift, how can I convert a String to CGFloat?

I tried:

var fl: CGFloat = str as CGFloat
var fl: CGFloat = (CGFloat)str
var fl: CGFloat = CGFloat(str)

all didn't work

If you want a safe way to do this, here is a possibility:

let str = "32.4"
if let n = NumberFormatter().number(from: str) {
    let f = CGFloat(truncating: n)
}

If you change str to "bob", it won't get converted to a float, while most of the other answers will get turned into 0.0

Side note: remember also that decimal separator might be either comma or period. You might want to specify it inside the number formatter

let formatter = NumberFormatter()
formatter.decimalSeparator = "." // or ","

// use formatter (e.g. formatter.number(from:))

As of Swift 2.0, the Double type has a failable initializer that accepts a String. So the safest way to go from String to CGFloat is:

let string = "1.23456"
var cgFloat: CGFloat?

if let doubleValue = Double(string) {
    cgFloat = CGFloat(doubleValue)
}

// cgFloat will be nil if string cannot be converted

If you have to do this often, you can add an extension method to String:

extension String {
  
  func CGFloatValue() -> CGFloat? {
    guard let doubleValue = Double(self) else {
      return nil
    }
    
    return CGFloat(doubleValue)
  }
}

Note that you should return a CGFloat? since the operation can fail.

You should cast string to double and then cast from double to CGFloat, Let try this:

let fl: CGFloat = CGFloat((str as NSString).doubleValue)

This works:

let str = "3.141592654"
let fl = CGFloat((str as NSString).floatValue)

in Swift 3.0

if let n = NumberFormatter().number(from: string) {
  let f = CGFloat(n)
}

or this if you are sure that string meets all requirements

let n = CGFloat(NumberFormatter().number(from: string)!)

While the other answers are correct, but the result you see will have trailing decimals.

For example:

let str = "3.141592654"
let foo = CGFloat((str as NSString).floatValue)

Result:

3.14159274101257

To get a proper value back from the string, try the following:

let str : String = "3.141592654"
let secStr : NSString = str as NSString
let flt : CGFloat = CGFloat(secStr.doubleValue)

Result:

3.141592654

You can make an extension that adds an init to CGFloat

extension CGFloat {
    
    init?(string: String) {
        
        guard let number = NumberFormatter().number(from: string) else {
            return nil
        }
        
        self.init(number.floatValue)
    }
    
}

Use it like so let x = CGFloat(xString)

Simple one line solution:

let pi = CGFloat(Double("3.14") ?? 0)

in Swift 3.1

if let n = NumberFormatter().number(from: string) {
   let fl = CGFloat(n)
} 

or:

let fl = CGFloat((str as NSString).floatValue))

This is kind of a work around, but you can cast it as an NSString, then get the float value, then initialize a CGFloat from that value. Example:

let str = "1.02345332"
let foo = CGFloat((str as NSString).floatValue)

Good question. There is not in fact any pure Swift API for converting a string that represents a CGFloat into a CGFloat. The only string-represented number that pure Swift lets you convert to a number is an integer. You'll have to use some other approach from some other library - for example, start with Foundation's NSString or C's (Darwin's) strtod.

let myFloatNumber = CGFloat("4.22")