新人，求解，

我根据环信开发视频，按照循序逐步进行操作，所有的依赖库也加了，但是仍让报这样的错误！求有经验的人帮助。


duplicate symbol _OBJC_IVAR_$_AppDelegate._window in:
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-346A44728D6FC995.o
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-421C04AF9DADCB8C.o
duplicate symbol _OBJC_METACLASS_$_AppDelegate in:
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-346A44728D6FC995.o
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-421C04AF9DADCB8C.o
duplicate symbol _OBJC_CLASS_$_AppDelegate in:
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-346A44728D6FC995.o
/Users/kuaiditu/Library/Developer/Xcode/DerivedData/ChatDemo-ggaeowmehkiyoiemeqphwqrlhkzv/Build/Intermediates/ChatDemo.build/Debug-iphonesimulator/ChatDemo.build/Objects-normal/x86_64/AppDelegate-421C04AF9DADCB8C.o
ld: 3 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)