How do I draw NSAttributedString in iOS5? - ios5

Question

When I try to draw an NSAttributedString and run it in iOS5 simulator I get a crash. In iOS6 it runs fine. I don't understand what I am doing wrong, because from what I read my code should also work on iOS5. My setup:
xCode 4.6.2
iOS 6.1 SDK
iOS 5.1 deployment target
I run the following code:
- (void)drawRect:(CGRect)rect
{
NSDictionary *txtAttr = #{
(NSString *)kCTFontAttributeName : [UIFont boldSystemFontOfSize:16]
};
NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:#"foobar" attributes:txtAttr];
CGContextRef ctx = UIGraphicsGetCurrentContext();
// flip context
CGContextSaveGState(ctx);
CGContextTranslateCTM(ctx, 0, self.bounds.size.height);
CGContextScaleCTM(ctx, 1, -1);
// I get a crash on the line below
CTLineRef line = CTLineCreateWithAttributedString(
(__bridge CFAttributedStringRef)string
);
CGContextSetTextPosition(ctx, 0, 4);
CTLineDraw(line, ctx);
CFRelease(line);
CGContextRestoreGState(ctx);
}
This crashes on CTLineCreateWithAttributedString with the stack trace:
#0 0x00140c68 in TAttributes::TAttributes(__CFDictionary const*) ()
#1 0x0011c499 in TTypesetterAttrString::Initialize(__CFAttributedString const*) ()
#2 0x0011c313 in TTypesetterAttrString::TTypesetterAttrString(__CFAttributedString const*) ()
#3 0x0010db14 in CTLineCreateWithAttributedString ()
#4 0x00065e5f in -[AttributedLabel drawRect:] at AttributedLabel.m:77
#5 0x003c8bd3 in -[UIView(CALayerDelegate) drawLayer:inContext:] ()
#6 0x002a7963 in -[CALayer drawInContext:] ()
#7 0x002b9f80 in backing_callback(CGContext*, void*) ()
#8 0x001d83fd in CABackingStoreUpdate_ ()
#9 0x002b9e2e in CA::Layer::display_() ()
#10 0x002a7a3d in -[CALayer _display] ()
#11 0x002adfd5 in CA::Layer::display() ()
#12 0x002a7a63 in -[CALayer display] ()
#13 0x002b19ae in CA::Layer::display_if_needed(CA::Transaction*) ()
#14 0x00236509 in CA::Context::commit_transaction(CA::Transaction*) ()
#15 0x002383f6 in CA::Transaction::commit() ()
#16 0x00237ad0 in CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) ()
#17 0x0140c99e in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ ()
#18 0x013a3640 in __CFRunLoopDoObservers ()
#19 0x0136f4c6 in __CFRunLoopRun ()
#20 0x0136ed84 in CFRunLoopRunSpecific ()
#21 0x0136ec9b in CFRunLoopRunInMode ()
#22 0x018157d8 in GSEventRunModal ()
#23 0x0181588a in GSEventRun ()
#24 0x0038a626 in UIApplicationMain ()
The place where the crash happens is shown below:
0x140c5a: calll 0x11c812 ; TCFRetained<__CFDictionary const*>::Retain(__CFDictionary const*)
0x140c5f: movl 8(%ebp), %eax
0x140c62: movl 4(%eax), %eax
0x140c65: movl 20(%eax), %eax
0x140c68: movl 8(%eax), %eax ;I get a Thread 1: EXC_BAD_ACCESS (code=2, address=0x08) here
0x140c6b: testl %eax, %eax
0x140c6d: je 0x140d0c ; TAttributes::TAttributes(__CFDictionary const*) + 482

Answer 1

The mistake is to use UIFont. iOS5 expects a CTFont, which is a Core Foundation type. Below is the code I used to get it working:
CTFontRef font = CTFontCreateWithName((CFStringRef)#"HelveticaNeue-Bold", 16, NULL);
NSDictionary *txtAttr = #{
(NSString *)kCTFontAttributeName : (id)CFBridgingRelease(font)
};
Use your font book app to locate the font and use the PostScript name. I would not have figured out this if I had not read: NSAttributedString in CATextLayer causes EXC_BAD_ACCESS (ios 5.0)

Answer 2

I don't know if you want to draw text line by line but here is my code that I used to draw NSAttributedString on a custom UIView:
I changed the code according to your attributed string:
- (void)drawRect:(CGRect)rect {
NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:#"yourString"];
UIFont *font = [UIFont boldSystemFontOfSize:16];
CTFontRef fontR = CTFontCreateWithName((CFStringRef)font.fontName, font.pointSize, NULL);
[attrString addAttribute:(NSString*)kCTFontAttributeName
value:(id)fontR
range:NSMakeRange(0, [yourText length])];
CFRelease(fontR);
CGMutablePathRef path = CGPathCreateMutable();
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrString);
// added 3 pixels at the top of the frame so that the text is not cuted
CGRect newRect = CGRectMake(rect.origin.x, rect.origin.y - 3, rect.size.width, rect.size.height);
CGPathAddRect(path, NULL, newRect);
CTFrameRef frameRef = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
CFRelease(framesetter);
CGPathRelease(path);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CTFrameDraw(frameRef, context);
CFRelease(frameRef);
[super drawRect:newRect];
}
I hope I didn't forgot anything, because I also perform some calculations on the attributed text and I removed them for a better example.
Hope this helps ;)