我也有类似的问题。在_OBJC_CLASS_$_后面的类名实际上是我的类。原因是我没有勾选“添加到目标”，当我拖动源代码文件到导航列表。

我的解决方案是:

从导航列表中删除类，并选择“仅删除引用” 再次拖动源代码文件，并确保“添加到目标”复选框被勾选。复选框就在“需要时复制”和“创建组”下面。

目标中可能缺少一些类。这通常发生在你重命名/删除/添加新的类文件到你的项目。若要修复，请将新添加的类添加到某些目标。

在Project Navigator中选择类(右侧栏)，打开Utilities侧栏(右侧栏)，从Utilities中选择File Inspector (File like icon)，在Target Membership选项卡下勾选你的目标。这都是为了避免“删除引用”，并再次添加“添加到目标”的技巧。

所以:选择Class -> Utilities (File Inspector) -> Target Membership ->勾选你想要的目标。

另一个可能导致“未定义符号”链接错误的原因是试图从.mm文件调用C函数。在这种情况下，您需要使用extern“C”{…}当您导入头文件时。

从objective - c++调用C-Function链接器错误

我还通过拖放添加了文件。我所做的，我删除了所有文件的引用(不包括框架)，然后通过添加文件到项目选项正确地添加它们，问题消失了。

我在.h文件中有多个@接口，还没有包括所有相应的@实现指令。确保它们都平衡了。

常见的原因

导致“架构armv7中未定义的符号”的常见原因有:

You import a header and do not link against the correct library. This is common, especially for headers for libraries like QuartzCore since it is not included in projects by default. To resolve: Add the correct libraries in the Link Binary With Libraries section of the Build Phases. If you want to add a library outside of the default search path you can include the path in the Library Search Paths value in the Build Settings and add -l{library_name_without_lib_and_suffix} (eg. for libz.a use -lz) to the Other Linker Flags section of Build Settings. You copy files into your project but forgot to check the target to add the files to. To resolve: Open the Build Phases for the correct target, expand Compile Sources and add the missing .m files. If this is your issue please upvote Cortex's answer below as well. You include a static library that is built for another architecture like i386, the simulator on your host machine. To resolve: If you have multiple library files from your libraries vendor to include in the project you need to include the one for the simulator (i386) and the one for the device (armv7 for example). Optionally, you could create a fat static library that contains both architectures.

最初的回答:

您没有链接到正确的libz文件。如果你右键点击该文件并在finder中显示它的路径应该在iOS sdk文件夹中的某个地方。这是我的例子

/开发/平台/ iPhoneOS.platform /开发/ sdk / iPhoneOS4.3.sdk / usr / lib

我建议删除引用，然后在目标的构建阶段Link Binary With Libraries部分重新添加它。