Cocoa editing NSBezierPath

Question

I have a simple bezierPath with 2 elements in a NSView; I want to modify the last element (NSPoint) on a button pressed but my code don't have any visual effect on the path. Here my code in NSView subclass:

    NSBezierPath *path;    
    - (void)drawRect:(NSRect)dirtyRect {
        [super drawRect:dirtyRect];
        // Drawing code here.

        path = [NSBezierPath bezierPath];
        [path moveToPoint:NSMakePoint(0, 0)];
        [path lineToPoint:NSMakePoint(60, 60)];
        [path setLineWith:2.0];
        [[NSColor redColor] set];
        [path stroke]; 
        //the path is correctly drawing and visible
    }

    - (IBAction)buttonPressed:(id)sender {
        NSPoint newPoint = NSMakePoint(120, 120);
        [path setAssociatedPoints:&newPoint atIndex:1]; //has no visible effect
   }

any suggestion ?

score 1 · Accepted Answer · answered Dec 31 '14 at 10:22

1

Every time you call drawRect: you are creating a new path and drawing it. Then, on the button press you modify the path.

So you have 2 problems:

You keep recreating the path - just create it once when the view is created
You don't redraw the view when the path is updated - use setNeedsDisplay

answered Dec 31 '14 at 10:22

Wain

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thank you for the support. I solved adding setNeedsDisplay:YES – mattiad Jan 02 '15 at 20:10

score 0 · Answer 2 · answered Dec 31 '14 at 10:22

You are recreating the Bezier path each time through your -drawRect: method. So, it doesn't matter that you kept the last one and modified it. You are discarding that and creating a new one the next time your view draws.

Also, if your variable is really just declared outside of any curly braces ({ … }), then it's not an instance variable. It's just a file-scope global variable. That means it's shared by all instances of this view class.

Cocoa editing NSBezierPath

2 Answers2