Objective-C—— undefined symbol

Question

我正在尝试在 cocoa touch 中使用渐变。我为此使用以下代码:

#import <QuartzCore/QuartzCore.h>

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = mainView.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor blackColor] CGColor], (id)[[UIColor whiteColor] CGColor], nil];
[mainView.layer insertSublayer:gradient atIndex:0];

但是当我尝试编译时出现以下错误:

Undefined symbols for architecture i386:
"_OBJC_CLASS_$_CAGradientLayer", referenced from: objc-class-ref in OfficeViewController.o ld: symbol(s) not found for architecture i386 collect2: ld returned 1 exit status

我试过清理但无济于事。不确定我还能做什么？

Answer 1

确保您确实在项目中包含了 QuartzCore 框架。它应该在 Link Binary With Libraries 阶段: