Two routines one in objective C, the other in Swift same code essentially different results - objective-c

Question

iOS 10.2 Swift 3.0
Trying to convert this code in objective C to Swift 3.0 and don't know the core graphics library too well.
#interface SPGripViewBorderView : UIView
#end
#implementation SPGripViewBorderView
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
// Clear background to ensure the content view shows through.
self.backgroundColor = [UIColor clearColor];
}
return self;
}
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
// (1) Draw the bounding box.
CGContextSetLineWidth(context, 1.0);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextAddRect(context, CGRectInset(self.bounds, kSPUserResizableViewInteractiveBorderSize/2, kSPUserResizableViewInteractiveBorderSize/2));
CGContextStrokePath(context);
// (2) Calculate the bounding boxes for each of the anchor points.
CGRect upperLeft = CGRectMake(0.0, 0.0, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect upperRight = CGRectMake(self.bounds.size.width - kSPUserResizableViewInteractiveBorderSize, 0.0, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect lowerRight = CGRectMake(self.bounds.size.width - kSPUserResizableViewInteractiveBorderSize, self.bounds.size.height - kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect lowerLeft = CGRectMake(0.0, self.bounds.size.height - kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect upperMiddle = CGRectMake((self.bounds.size.width - kSPUserResizableViewInteractiveBorderSize)/2, 0.0, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect lowerMiddle = CGRectMake((self.bounds.size.width - kSPUserResizableViewInteractiveBorderSize)/2, self.bounds.size.height - kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect middleLeft = CGRectMake(0.0, (self.bounds.size.height - kSPUserResizableViewInteractiveBorderSize)/2, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
CGRect middleRight = CGRectMake(self.bounds.size.width - kSPUserResizableViewInteractiveBorderSize, (self.bounds.size.height - kSPUserResizableViewInteractiveBorderSize)/2, kSPUserResizableViewInteractiveBorderSize, kSPUserResizableViewInteractiveBorderSize);
// (3) Create the gradient to paint the anchor points.
CGFloat colors [] = {
0.4, 0.8, 1.0, 1.0,
0.0, 0.0, 1.0, 1.0
};
CGColorSpaceRef baseSpace = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 2);
CGColorSpaceRelease(baseSpace), baseSpace = NULL;
// (4) Set up the stroke for drawing the border of each of the anchor points.
CGContextSetLineWidth(context, 1);
CGContextSetShadow(context, CGSizeMake(0.5, 0.5), 1);
CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
// (5) Fill each anchor point using the gradient, then stroke the border.
CGRect allPoints[8] = { upperLeft, upperRight, lowerRight, lowerLeft, upperMiddle, lowerMiddle, middleLeft, middleRight };
for (NSInteger i = 0; i < 8; i++) {
CGRect currPoint = allPoints[i];
CGContextSaveGState(context);
CGContextAddEllipseInRect(context, currPoint);
CGContextClip(context);
CGPoint startPoint = CGPointMake(CGRectGetMidX(currPoint), CGRectGetMinY(currPoint));
CGPoint endPoint = CGPointMake(CGRectGetMidX(currPoint), CGRectGetMaxY(currPoint));
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGContextStrokeEllipseInRect(context, CGRectInset(currPoint, 1, 1));
}
CGGradientRelease(gradient), gradient = NULL;
CGContextRestoreGState(context);
}
#end
Which I re-coded as this ...
import UIKit
class GripViewBorderView: UIView {
let kUserResizableViewInteractiveBorderSize:CGFloat = 10.0
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override init(frame: CGRect) {
super.init(frame: frame)
}
override func draw(_ rect:CGRect) {
let context = UIGraphicsGetCurrentContext();
context!.saveGState();
// (1) Draw the bounding box.
context!.setLineWidth(1.0);
context!.setStrokeColor(UIColor.blue.cgColor)
//CGContextAddRect(context!, CGRectInset(self.bounds, (kSPUserResizableViewInteractiveBorderSize / 2.0), (kSPUserResizableViewInteractiveBorderSize / 2.0)));
context!.addRect(self.bounds.insetBy(dx: (kUserResizableViewInteractiveBorderSize / 2.0), dy: (kUserResizableViewInteractiveBorderSize / 2.0)))
context!.strokePath();
// (2) Calculate the bounding boxes for each of the anchor points.
let upperLeft = CGRect(x: 0.0, y: 0.0, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize)
let upperRight = CGRect(x: self.bounds.size.width - kUserResizableViewInteractiveBorderSize, y: 0.0, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let lowerRight = CGRect(x: self.bounds.size.width - kUserResizableViewInteractiveBorderSize, y: self.bounds.size.height - kUserResizableViewInteractiveBorderSize, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let lowerLeft = CGRect(x: 0.0, y: self.bounds.size.height - kUserResizableViewInteractiveBorderSize, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let upperMiddle = CGRect(x: (self.bounds.size.width - kUserResizableViewInteractiveBorderSize)/2, y: 0.0, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let lowerMiddle = CGRect(x: (self.bounds.size.width - kUserResizableViewInteractiveBorderSize)/2, y: self.bounds.size.height - kUserResizableViewInteractiveBorderSize, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let middleLeft = CGRect(x: 0.0, y: (self.bounds.size.height - kUserResizableViewInteractiveBorderSize)/2, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
let middleRight = CGRect(x: self.bounds.size.width - kUserResizableViewInteractiveBorderSize, y: (self.bounds.size.height - kUserResizableViewInteractiveBorderSize)/2, width: kUserResizableViewInteractiveBorderSize, height: kUserResizableViewInteractiveBorderSize);
// (3) Create the gradient to paint the anchor points.
let baseSpace = CGColorSpaceCreateDeviceRGB()
//let gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 2)
let colors = [UIColor.red.cgColor,
UIColor.yellow.cgColor]
let gradient = CGGradient(colorsSpace: baseSpace, colors: colors as CFArray, locations: nil)
// (4) Set up the stroke for drawing the border of each of the anchor points.
context!.setLineWidth(1)
context!.setShadow(offset: CGSize(width: 0.5, height: 0.5), blur: 1)
context!.setStrokeColor(UIColor.white.cgColor)
// (5) Fill each anchor point using the gradient, then stroke the border.
let allPoints:[CGRect] = [ upperLeft, upperRight, lowerRight, lowerLeft, upperMiddle, lowerMiddle, middleLeft, middleRight ];
for i in 0 ... 7 {
let currPoint = allPoints[i]
context!.saveGState()
context!.addEllipse(in: currPoint)
context!.clip()
let startPoint = CGPoint(x: currPoint.midX, y: currPoint.minY);
let endPoint = CGPoint(x: currPoint.midX, y: currPoint.maxY);
context!.drawLinearGradient(gradient!, start: startPoint, end: endPoint, options: .init(rawValue: 0))
context!.saveGState()
context!.strokeEllipse(in: currPoint.insetBy(dx: 1, dy: 1))
}
context!.restoreGState()
}
}
But I missed something cause the OOC is on the left and my new Swift on the right. For reasons I cannot figure I get only a single dot drawn in my version, the OOC version draws 8 dots [correctly].

Answer 1

You have written context!.saveGState() at the end of the for loop in place of CGContextRestoreGState(context). It should, of course, be context!.restoreGState(). Simple typo!
Also, please remove all of the semi-colons, and use guard let context = UIGraphicsGetCurrentContext() else { return } to get rid of all those forced unwrappings!