我收到以下链接器错误：
Ld /Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Products/Debug-iphonesimulator/Tweepr.app/Tweepr normal x86_64
cd /Users/premedios/Developer/Objective-C/tweepr-3
export IPHONEOS_DEPLOYMENT_TARGET=6.0
export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.1.sdk -L/Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Products/Debug-iphonesimulator -F/Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Products/Debug-iphonesimulator -F/Users/premedios/Developer/Objective-C/tweepr-3/iUnfollow/Classes/Library -filelist /Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Intermediates/Tweepr.build/Debug-iphonesimulator/Tweepr.build/Objects-normal/x86_64/Tweepr.LinkFileList -Xlinker -objc_abi_version -Xlinker 2 -ObjC -fobjc-arc -fobjc-link-runtime -Xlinker -no_implicit_dylibs -mios-simulator-version-min=6.0 -framework Accelerate -framework Social -framework Security -framework StoreKit -framework ImageIO -framework MapKit -framework CoreText -framework CoreTelephony -lz -framework MobileCoreServices -framework Accounts -framework Twitter -framework CoreData -framework SystemConfiguration -framework CoreFoundation -framework CFNetwork -framework UIKit -framework Foundation -framework CoreGraphics -framework QuartzCore -lPods -Xlinker -dependency_info -Xlinker /Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Intermediates/Tweepr.build/Debug-iphonesimulator/Tweepr.build/Objects-normal/x86_64/Tweepr_dependency_info.dat -o /Users/premedios/Library/Developer/Xcode/DerivedData/Tweepr-chpytouktuxjlfehpsynwphlgwzo/Build/Products/Debug-iphonesimulator/Tweepr.app/Tweepr
Undefined symbols for architecture x86_64:
"_OBJC_CLASS_$_STTwitterAPI", referenced from:
objc-class-ref in NetworkManager.o
"_OBJC_CLASS_$_SVProgressHUD", referenced from:
objc-class-ref in Utils.o
objc-class-ref in NetworkManager.o
objc-class-ref in TPRIAPManager.o
"_OBJC_CLASS_$_SimpleAuth", referenced from:
objc-class-ref in TPRAppDelegate.o
objc-class-ref in UserLoadingRoutine.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
我尝试了＃34; Clean Build Folder＆＃34;，但错误仍然存在。任何人对此的原因都有任何其他想法吗？