Xcode链接器错误编写Objective-C

Question

我的一个朋友让我尽可能用objective-c重写Box2D。我开始写作，到目前为止，当我构建项目时，我遇到了一些链接器错误，我以前遇到过类似的问题，但这没有帮助。我得到的错误是：

Ld /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug/Obj-Box2D normal x86_64
    cd /Users/aizen-qa/Desktop/Obj-Box2D
    setenv MACOSX_DEPLOYMENT_TARGET 10.9
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -L/Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug -F/Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug -filelist /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Obj-Box2D.LinkFileList -mmacosx-version-min=10.9 -fobjc-arc -fobjc-link-runtime -framework Foundation -Xlinker -dependency_info -Xlinker /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Obj-Box2D_dependency_info.dat -o /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Products/Debug/Obj-Box2D

duplicate symbol _Ob2IsValid in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Mat22.o
duplicate symbol _Ob2InvSqr in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Mat22.o
duplicate symbol _Ob2IsValid in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec2.o
duplicate symbol _Ob2InvSqr in:
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec3.o
    /Users/aizen-qa/Library/Developer/Xcode/DerivedData/Obj-Box2D-bwsosdvwkjzsscahpbqrbrnzlall/Build/Intermediates/Obj-Box2D.build/Debug/Obj-Box2D.build/Objects-normal/x86_64/Ob2Vec2.o
ld: 4 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我读过类似的问题，并尝试了检查导入不使用.m和重复变量名等解决方案。但是我注意到向量的类具有相同的实例变量名称，x，y 所以这是我得到错误的原因吗？

Answer 1

您在多个实现文件中定义而不是声明数据元素。这通常是因为包含的标头中的某些内容。

查找引用 Ob2InvSqr 或 Ob2IsValid 的位置，并确保这些项目的存储只完成一次。

Answer 2

文件 Ob2Vec2.o 和 Ob2Vec3.o 包含相同的符号 _Ob2InvSqr

这很可能意味着您在同一个目标中同时拥有 Ob2Vec2.m 和 Ob2Vec3.m。

确保只有一个被真正编译

Answer 3

我猜你的一个头文件中有一个内联函数 _Ob2IsValid(...) 没有被内联（它太大了吗？）

如果是这种情况，您可以像这样强制它内联：

__attribute__((always_inline)) inline void MyFunction(...) {}

或者只是让它脱线

Answer 4

感谢 MartinR 的评论表，我能够解决这个问题。这是因为我在一个包含在多个 Objective-C 类中的 .h 文件中定义了一个函数。所以我所做的就是将函数头放在 .h 文件中，并将其实现放在 .m 文件中。