Objective-C - 未定义的符号 [英] Objective-C – Undefined symbols

问题描述

我想在可可触摸中使用渐变。我使用以下代码：

I'm trying to use a gradient in cocoa touch. I'm using the following code for this:

#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会出现以下错误：

But I get the following error when I try to compile:

架构i386的未定义符号：

_OBJC_CLASS _ $ _ CAGradientLayer，引用自：
OfficeViewController.o中的objc-class-ref ld：找不到符号
for architecture i386 collect2：ld returned 1 exit status

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

干净无济于事。不确定我还能做什么？

I've tried to do a clean to no avail. Not really sure what else I can do?

推荐答案

确保你实际上在项目中包含QuartzCore框架。它应该在链接二进制与库的阶段：

Make sure you actually included the QuartzCore framework in your project. It should be in the Link Binary With Libraries phases:

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