How to draw a rectangle? - iphone

Question

I want to draw a filled rectangle in my viewContoller's view.
I wrote the code below in viewDidLoad. But there is no change.
What is wrong?
CGRect rectangle = CGRectMake(0, 100, 320, 100);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextFillRect(context, rectangle);

Answer 1

You can't do it in a viewController.
You need to extend your View and add the code under "drawRect:"
this will change the drawing logic of your view.
-(void) drawRect:(CGRect)rect{
[super drawRect:rect];
CGRect rectangle = CGRectMake(0, 100, 320, 100);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextFillRect(context, rectangle);
}

Answer 2

modern 2018 solution..
override func draw(_ rect: CGRect) {
let r = CGRect(x: 5, y: 5, width: 10, height: 10)
UIColor.yellow.set()
UIRectFill(r)
}
that's it.

Answer 3

Just for clarity:
If You need to draw a rectangle which has the same fill and border color, then You can replace:
CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
with:
[[UIColor redColor] set];

Answer 4

You can't render directly in viewDidLoad; it's the views themselves that would have to run this in their drawRect method.
The easiest way to "draw" a rectangle is to place a UIView with a background color & border in your view. (You can set the border via the view's CALayer's methods. i.e. myView.layer.borderColor = [[UIColor redColor] CGColor];)