我对Xcode还是很陌生，一直在进行一项研究，因为我需要它来学习。我正在为AP Comp Sci课程的最终项目制作应用程序。我想知道是否有人对此错误消息的错误可能在哪里：
Ld /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Products/Debug-iphonesimulator/BTOS.app/BTOS normal x86_64 (in target: BTOS) cd /Users/AshleyHamilton/Desktop/BTOS export IPHONEOS_DEPLOYMENT_TARGET=12.2 /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/iPhoneSimulator12.2.sdk -L/Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Products/Debug-iphonesimulator -F/Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Products/Debug-iphonesimulator -filelist /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Intermediates.noindex/BTOS.build/Debug-iphonesimulator/BTOS.build/Objects-normal/x86_64/BTOS.LinkFileList -Xlinker -rpath -Xlinker /usr/lib/swift -Xlinker -rpath -Xlinker @executable_path/Frameworks -mios-simulator-version-min=12.2 -dead_strip -Xlinker -object_path_lto -Xlinker /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Intermediates.noindex/BTOS.build/Debug-iphonesimulator/BTOS.build/Objects-normal/x86_64/BTOS_lto.o -Xlinker -export_dynamic -Xlinker -no_deduplicate -Xlinker -objc_abi_version -Xlinker 2 -fobjc-link-runtime -L/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator -Xlinker -add_ast_path -Xlinker /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Intermediates.noindex/BTOS.build/Debug-iphonesimulator/BTOS.build/Objects-normal/x86_64/BTOS.swiftmodule -Xlinker -sectcreate -Xlinker __TEXT -Xlinker __entitlements -Xlinker /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Intermediates.noindex/BTOS.build/Debug-iphonesimulator/BTOS.build/BTOS.app-Simulated.xcent -Xlinker -dependency_info -Xlinker /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Intermediates.noindex/BTOS.build/Debug-iphonesimulator/BTOS.build/Objects-normal/x86_64/BTOS_dependency_info.dat -o /Users/AshleyHamilton/Library/Developer/Xcode/DerivedData/BTOS-fwvvqofheqlokcazrsdkgqhnnzjg/Build/Products/Debug-iphonesimulator/BTOS.app/BTOS ld: entry point (_main) undefined. for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)
我很沮丧，并尝试了在几个不同站点上发现的许多方法。