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castingswiftcgfloat
Andrew Ebling
Andrew Ebling

Reputation: 10283

Casting CGFloat to Float in Swift

I need to store a value as a Float, but the source data is a CGFloat:

let myFloat : Float = myRect.origin.x

but this results in the compiler error: 'NSNumber' is not of subtype 'Float'

So if I explicitly cast it like this:

let myFloat : Float = myRect.origin.x as Float

but this in turn results in the compiler error: 'Cannot convert the expression's type 'Float' to 'Float''

What's the correct way to do this and satisfy the compiler please?

Upvotes: 104

Views: 94324

Answers (3)

hyouuu
hyouuu

Reputation: 2491

If you are as lazy as I am, in an Extensions.swift define the following:

extension Int {
  var f: CGFloat { return CGFloat(self) }
}

extension Float {
  var f: CGFloat { return CGFloat(self) }
}

extension Double {
  var f: CGFloat { return CGFloat(self) }
}

extension CGFloat {
  var swf: Float { return Float(self) }
}

Then you can do:

var someCGFloatFromFloat = 1.3.f
var someCGFloatFromInt = 2.f
var someFloatFromCGFloat = someCGFloatFromFloat.swf

Upvotes: 34

Erik
Erik

Reputation: 12858

You can use the Float() initializer:

let cgFloat: CGFloat = 3.14159
let someFloat = Float(cgFloat)

Upvotes: 199

Sulthan
Sulthan

Reputation: 130102

Usually, the best solution is to keep the type and use CGFloat, even in Swift. That's because CGFloat has different size on 32bit and 64bit machines.

Keyword as can be used only for dynamic casting (for subclasses), e.g.

class A {
}

class B : A {
}

var a: A = B()
var b: B = a as B

However, Double, Int, Float etc are not subclasses of each other, therefore to "cast" you have to create a new instance, e.g.

var d: Double = 2.0
var f: Float = Float(d) //this is an initialiser call, not a cast
var i: Int = Int(d) //this is an initialiser call, not a cast

Upvotes: 13

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