如何在swift中将Int32值转换为CGFloat？

Question

Here my code. I am passing two values into CGRectMake(..) and getting and error.

let width = CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).width
// return Int32 value

let height = CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).height
// return Int32 value

myLayer?.frame = CGRectMake(0, 0, width, height)
// returns error: '`Int32`' not convertible to `CGFloat`

How can I convert Int32 to CGFloat to not return an error?

Answer 1

To convert between numerical data types create a new instance of the target type, passing the source value as parameter. So to convert an Int32 to a CGFloat :

let int: Int32 = 10
let cgfloat = CGFloat(int)

In your case you can either do:

let width = CGFloat(CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).width)
let height = CGFloat(CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).height)

myLayer?.frame = CGRectMake(0, 0, width, height)

or:

let width = CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).width
let height = CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription as CMVideoFormatDescriptionRef!).height

myLayer?.frame = CGRectMake(0, 0, CGFloat(width), CGFloat(height))

Note that there is no implicit or explicit type casting between numeric types in swift, so you have to use the same pattern also for converting a Int to Int32 or to UInt etc.

Answer 2

只需使用CGFloat's初始化程序将width和height显式转换为CGFloat ：

myLayer?.frame = CGRectMake(0, 0, CGFloat(width), CGFloat(height))