一个Xcode初学者的问题:

这是我第一次使用Xcode 4.6.3。

我试图写一个非常简单的控制台程序,搜索配对的BT设备,并将它们打印到NSLog。

它会生成以下错误:

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_IOBluetoothDevice", referenced from:
      objc-class-ref in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我疯狂地搜索。常见的问题应该是对文件的引用,其中只有头文件被导入,链接器没有找到任何实现(*.m-file)。IOBluetooth库是一个标准框架,就像基础框架一样。

我在上面的陈述中遗漏了什么?

我还尝试为32位机器构建它(构建再次失败)。这显然是一个链接器错误,但我不知道,它与什么有关,除了有一个问题,找到IOBluetoothDevice的实现,在x86和x64架构上,而头文件是从一个标准包含的框架,称为IOBluetooth?

供你参考,我的主要代码是main。m”:

#import <Foundation/Foundation.h>
#import <IOBluetooth/objc/IOBluetoothDevice.h>          // Note the import for bluetooth
#import <IOBluetooth/objc/IOBluetoothDeviceInquiry.h>   // Note the import for bluetooth


int main(int argc, const char * argv[])
{
    @autoreleasepool {
        IOBluetoothDevice *currentDevice;
        NSArray *devices = [ IOBluetoothDevice pairedDevices];


        for (id currentDevice in devices){
          NSLog(@"%i : %@",[ currentDevice classOfDevice ], [ currentDevice name ]);    
        }
    }
    return 0;
}

谢谢你的任何帮助或指点正确的方向。


当前回答

If you're getting this error when trying to link to a C file, first double check the function names for typos. Next double check that you are not trying to call a C function from a C++ / Objective-C++ environment without using the extern C {} construct. I was tearing my hair out because I had a class that was in a .mm file which was trying to call C functions. It doesn't work because in C++, the symbols are mangled. You can actually see the concrete symbols generated using the nm tool. Terminal to the path of the .o files, and run nm -g on the file that is calling the symbol and the one that should have the symbol, and you should see if they match up or not, which can provide clues for the error.

nm -g file.o

你可以这样检查c++符号:

nm -gC file.o

其他回答

If you're getting this error when trying to link to a C file, first double check the function names for typos. Next double check that you are not trying to call a C function from a C++ / Objective-C++ environment without using the extern C {} construct. I was tearing my hair out because I had a class that was in a .mm file which was trying to call C functions. It doesn't work because in C++, the symbols are mangled. You can actually see the concrete symbols generated using the nm tool. Terminal to the path of the .o files, and run nm -g on the file that is calling the symbol and the one that should have the symbol, and you should see if they match up or not, which can provide clues for the error.

nm -g file.o

你可以这样检查c++符号:

nm -gC file.o

架构x86_64的未定义符号:"_OBJC_CLASS_$_xxx", 引用: yyy.o中的Objc-class-ref

这通常意味着,您从类“yyy”中调用“xxx”(它可能是一个框架或类)。编译器无法定位“xxx”,因此出现此错误。

你需要添加丢失的文件(在本例中是“xxx”),右键单击导航窗口中的项目文件夹,点击“将文件添加到“YourProjectName”选项。

一个弹出窗口将打开Finder中的项目文件。在那里,您可以看到丢失的文件,并将它们添加到您的项目中。不要忘记勾选“需要时复制项目”框。祝你好运! !

我通过在构建设置中的其他链接器标志中添加“-lc++”来解决这个问题。

I have found this can also occur if you drag a folder with Objective-C files into your project. If that folder appears blue I think it indicates its not properly linked. You can verify this (if you use version control) because whenever you add new files the pbxproj file should update with links to those new files. However you may find that after you added a folder that the pbxproj file did not change (and hence there is a linking error). So you will get auto-complete working and it will find the classes you imported, but when it goes to actually build the image it fails with this error code.

解决方案是不添加文件夹,而是添加文件。这样做,您应该会看到pbxproj文件更新,它应该会修复这个错误。

这还假定您已经完成了上面建议的操作,并正确链接了所有正确的框架。

有时,我忘记从Release-universal复制库,并错误地从Release-iphoneos复制。通常Release-iphoneos包含。a文件,该文件已为X86裁剪。所以它给出了误差。