Xcode 6.1
OS X 10.9.5
Swift Mac Document-based Application target
I am using Swift to make a Cocoa Mac app (NOT iOS!). I have a custom NSView
subclass. I'd like to override -drawRect:
, and access the current CGContext
to do some drawing using the CoreGraphics APIs.
However, I can't seem to access the current CGContext
in Swift (something I've done hundreds of times in ObjC). Here's my code:
import Cocoa
class Canvas: NSView {
override func drawRect(dirtyRect: CGRect) {
if let ctx: CGContext! = NSGraphicsContext.currentContext()?.CGContext {
// do drawing
}
}
}
When I run, I get an immediate crash on the first line of my drawRect
implementation:
-[NSWindowGraphicsContext CGContext]: unrecognized selector sent to instance 0x60800005e840
What am I doing wrong? How do I fetch the current CGContext
for drawing in Swift?
I definitely want to use the CoreGraphics API. Unless using the CoreGraphics API in Swift is entirely impossible, please do not respond with suggestions on how to use AppKit drawing APIs instead (I don't care if they are easier). I want to know how to use CoreGraphics from Swift on OS X.
Example
Swift 3+
class CustomView: NSView {
private var currentContext : CGContext? {
get {
if #available(OSX 10.10, *) {
return NSGraphicsContext.current?.CGContext
} else if let contextPointer = NSGraphicsContext.currentContext()?.graphicsPort {
let context: CGContextRef = Unmanaged.fromOpaque(COpaquePointer(contextPointer)).takeUnretainedValue()
return context
}
return nil
}
}
private func saveGState(drawStuff: (ctx:CGContextRef) -> ()) -> () {
if let context = self.currentContext {
CGContextSaveGState (context)
drawStuff(ctx: context)
CGContextRestoreGState (context)
}
}
override func drawRect(dirtyRect: NSRect) {
super.drawRect(dirtyRect)
saveGState { ctx in
// Drawing code here.
}
}
}
Swift 2
class CustomView: NSView {
private var currentContext : CGContext? {
get {
if #available(OSX 10.10, *) {
return NSGraphicsContext.currentContext()?.CGContext
} else if let contextPointer = NSGraphicsContext.currentContext()?.graphicsPort {
let context: CGContextRef = Unmanaged.fromOpaque(COpaquePointer(contextPointer)).takeUnretainedValue()
return context
}
return nil
}
}
private func saveGState(drawStuff: (ctx:CGContextRef) -> ()) -> () {
if let context = self.currentContext {
CGContextSaveGState (context)
drawStuff(ctx: context)
CGContextRestoreGState (context)
}
}
override func drawRect(dirtyRect: NSRect) {
super.drawRect(dirtyRect)
saveGState { ctx in
// Drawing code here.
}
}
}