Confusion due to Swift lacking implicit conversion of CGFloat

swift types type-conversion cgfloat
Mani picture Mani · Jun 9, 2014 · Viewed 11.8k times · Source

Trying to do arithmetic in a function that returns `CGFloat, I get an error:

Couldn't find overload for '/' that accepts supplied arguments

func kDCControlDegreesToRadians(x : CGFloat) -> CGFloat
{ 
     return (M_PI * (x) / 180.0) // error is here. 
}

Has anyone else seen this type of issue?

Answer

Sulthan picture Sulthan · Jun 9, 2014

This is a problem with double to float conversion.

On a 64-bit machine, CGFloat is defined as double and you will compile it without problems because M_PI and x are both doubles.

On a 32-bit machine, CGFloat is a float but M_PI is still a double. Unfortunately, there are no implicit casts in Swift, so you have to cast explicitly:

return (CGFloat(M_PI) * (x) / 180.0)

The type for 180.0 literal is inferred.

In Swift 3

M_PI is deprecated, use CGFloat.pi instead:

return (x * .pi / 180.0)

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