Re: Why are some Core Graphics APIs "hidden" from Swift?
Re: Why are some Core Graphics APIs "hidden" from Swift?
- Subject: Re: Why are some Core Graphics APIs "hidden" from Swift?
- From: Quincey Morris <email@hidden>
- Date: Wed, 30 Aug 2017 15:42:42 -0700
On Aug 30, 2017, at 14:04 , Rick Mann <email@hidden> wrote:
>
> But the X, Y versions have a double underscore:
>
> CGContext.__addArc(x1: CGFloat, y1: CGFloat, x2: CGFloat, y2: CGFloat,
> radius: CGFloat)
>
> Why is this?
I believe the double-underscore prefix indicates an Obj-C API that is exposed
through Swift but not intended for general use. It may be that it’s there for
3rd party developers who insist on using that particular API, or it may be for
the Swift compiler to call through to. There is generally a better (simpler)
API that does the same thing.
In this case, it may be that the x/y plus 1/2 coordinate pattern is an outlier,
and Swift standardizes on points instead, in geometrical methods. You can pass
CGPoint(x: x1, y:y1) and CGPoint (x: x2, y: y2) into the other API. My guess is
that Swift generates the exact same code for the parameters in either case,
because it can *always* inline the CGPoint creation methods. You’re not paying
a performance or code size penalty, and you are gaining consistency.
I don’t know if my reasoning is correct, but it’s an argument that can be made
in other similar cases too, so I think it’s something like that.
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