Call to [UIColor colorWithRed:green:blue:alpha:] causing terrible crash

Question

Summary:

In subclass of UITextField:

• [UIColor colorWithRed:green:blue:alpha] causes total app crash
• [UIColor greenColor] works fine without any problems

How is that possible?

Answer:

As it turns out, the problem is that it was from layoutSubviews that I was calling the method that was using colorWithRed. Apparently colorWithRed allocates extra memory and that causes a problem at that point. (Thanks to Johannes Fahrenkrug for pointing out in a comment that it may well be something else -- see below.)

Detail:

In a ECTextField class that is a subclass of UITextField I get a terrible crash when I make the following call:

[self setTextColor:[UIColor colorWithRed:42/255.0 green:170/255.0 blue:42/255.0 alpha:0.8]];

The app freezes, hangs, and then after a little while I get the following error:

SampleApp(58375,0x34f71a8) malloc: *** mach_vm_map(size=1048576) failed (error code=3)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
2013-11-14 22:25:11.929 SampleApp[58375:907] *** Terminating app due to uncaught exception 'NSMallocException', reason: '*** NSAllocateObject(): attempt to allocate object of class 'NSPathStore2' failed'
*** First throw call stack:
(0x2362012 0x2166e7e 0x2361deb 0x1b5bcf2 0x1b60148 0x1bdb7a6 0x120f8a3 0x10ccaf2 0x96b14e4 0x10cc84e 0x96b1542 0x130c42 0x120491 0x120308 0x10fb2dd 0x217a6b0 0x3dbfc0 0x3d033c 0x3d0150 0x34e0bc 0x34f227 0x34f8e2 0x232aafe 0x232aa3d 0x23087c2 0x2307f44 0x2307e1b 0x35647e3 0x3564668 0x10aaffc 0x798d 0x25a5)
libc++abi.dylib: terminate called throwing an exception

Strangely enough everything works fine if I replace that line of code with the following:

[self setTextColor:[UIColor greenColor]];

Does anyone know why that might be, and what I could try to fix this problem?

Thanks for any help,

Erik

Answer 1

The problem is that you have an infinite loop. If you call [self setTextColor: in layoutSubviews of your UITextField subclass, you create an infinite loop because setTextColor causes layoutSubviews to be called again: UITextView setTextColor changes layout in UITableViewCell

That's why it takes a while for the error to appear: The app runs out of memory. You can probably verify this by running it with Instruments.

Never call anything from layoutSubviews that triggers layoutSubviews.

Answer 2

Change it to

[self setTextColor:[UIColor colorWithRed:42.0f/255.0f green:170.0f/255.0f blue:42.0f/255.0f alpha:0.8f]];

component of the color object, specified as a value from 0.0 to 1.0.

Answer 3

creating category for color is best. You can reuse your code at as many places you want.

How to create a category?

If you press command+n it will show you a file option Category. Choose from there or create a .h file named UIColor+custom.h and .m named UIColor+custom.m

In .m file define a method:

+ (UIColor *)myColor
{
    return [UIColor colorWithRed:42.0/255.0 green:170.0/255.0 blue:42.0/255.0  alpha:0.8];
}

and declare this method in .h file:

+ (UIColor *) myColor;

now import this category in your viewController like this:

#import "UIColor+custom.h"

and now give your UITextField text color like this:

[self setTextColor:[UIColor myColor]];

Hope this helps.