子类化 NSObject 和使用泛型时 Swift 编译错误
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【中文标题】子类化 NSObject 和使用泛型时 Swift 编译错误【英文标题】：Swift compile error when subclassing NSObject and using generics 【发布时间】：2014-06-11 11:17:12 【问题描述】：以下 Swift 代码在构建时生成编译错误：
import Foundation
class Wrapper<T> : NSObject
let obj : T
init(x : T)
self.obj = x
是我做错了什么还是编译器错误？
如果是这样，我可以做些什么来解决它？
错误日志：
CompileSwift normal i386 com.apple.xcode.tools.swift.compiler
cd /Users/hermespique/workspace/HanekeSwift
export PATH="/Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode6-Beta.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -target i386-apple-ios8.0 -module-name HanekeTests -O0 -sdk /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk -g -module-cache-path /Users/hermespique/Library/Developer/Xcode/DerivedData/ModuleCache -I /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator -F /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Library/Frameworks -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -c -j4 /Users/hermespique/workspace/HanekeSwift/HanekeTests/XCTestCase+Assert.swift /Users/hermespique/workspace/HanekeSwift/HanekeTests/Cache.swift /Users/hermespique/workspace/HanekeSwift/HanekeTests/Wrapper.swift -output-file-map /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/HanekeTests-OutputFileMap.json -serialize-diagnostics -emit-dependencies -emit-module -emit-module-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/HanekeTests.swiftmodule -Xcc -iquote -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-generated-files.hmap -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-own-target-headers.hmap -Xcc -ivfsoverlay -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/all-product-headers.yaml -Xcc -iquote -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-project-headers.hmap -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator/include -Xcc -I/Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/DerivedSources/i386 -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/DerivedSources -Xcc -DDEBUG=1 -Xcc -DDEBUG=1 -emit-objc-header -emit-objc-header-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/HanekeTests-Swift.h
0 swift 0x000000010a889608 llvm::sys::PrintStackTrace(__sFILE*) + 40
1 swift 0x000000010a889af4 SignalHandler(int) + 452
2 libsystem_platform.dylib 0x00007fff88e185aa _sigtramp + 26
3 libsystem_platform.dylib 0x00007fff55fb0334 _sigtramp + 3440999844
4 swift 0x0000000109c87395 swift::irgen::IRGenFunction::emitTypeMetadataRef(swift::CanType) + 21
5 swift 0x0000000109cbcfb8 (anonymous namespace)::OpaqueArchetypeTypeInfo::destroy(swift::irgen::IRGenFunction&, swift::irgen::Address, swift::CanType) const + 24
6 swift 0x0000000109cf467b swift::SILVisitor<(anonymous namespace)::IRGenSILFunction, void>::visit(swift::ValueBase*) + 23579
7 swift 0x0000000109cee266 swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 8678
8 swift 0x0000000109c6f6f8 swift::irgen::IRGenModule::emitGlobalTopLevel() + 184
9 swift 0x0000000109cdb6e3 performIRGeneration(swift::IRGenOptions&, swift::Module*, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, swift::SourceFile*, unsigned int) + 1859
10 swift 0x0000000109cdc033 swift::performIRGeneration(swift::IRGenOptions&, swift::SourceFile&, swift::SILModule*, llvm::StringRef, llvm::LLVMContext&, unsigned int) + 51
11 swift 0x0000000109c4e65a frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 4842
12 swift 0x0000000109c4d35d main + 1533
13 libdyld.dylib 0x00007fff8ddbb5fd start + 1
14 libdyld.dylib 0x0000000000000040 start + 1914980932
Stack dump:
0. Program arguments: /Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c /Users/hermespique/workspace/HanekeSwift/HanekeTests/XCTestCase+Assert.swift /Users/hermespique/workspace/HanekeSwift/HanekeTests/Cache.swift -primary-file /Users/hermespique/workspace/HanekeSwift/HanekeTests/Wrapper.swift -enable-objc-attr-requires-objc-module -target i386-apple-ios8.0 -module-name HanekeTests -sdk /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk -I /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator -F /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Library/Frameworks -F /Applications/Xcode6-Beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -g -module-cache-path /Users/hermespique/Library/Developer/Xcode/DerivedData/ModuleCache -Xcc -iquote -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-generated-files.hmap -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-own-target-headers.hmap -Xcc -ivfsoverlay -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/all-product-headers.yaml -Xcc -iquote -Xcc /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/HanekeTests-project-headers.hmap -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Products/Debug-iphonesimulator/include -Xcc -I/Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/DerivedSources/i386 -Xcc -I/Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/DerivedSources -Xcc -DDEBUG=1 -Xcc -DDEBUG=1 -emit-module-doc-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/Wrapper~partial.swiftdoc -O0 -emit-module-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/Wrapper~partial.swiftmodule -serialize-diagnostics-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/Wrapper.dia -emit-dependencies-path /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/Wrapper.d -o /Users/hermespique/Library/Developer/Xcode/DerivedData/Haneke-dsgqpxenngbaqpctbkhhwtqbiorj/Build/Intermediates/Haneke.build/Debug-iphonesimulator/HanekeTests.build/Objects-normal/i386/Wrapper.o
1. While emitting IR SIL function @_TToFC11HanekeTests7WrapperE for 'deinit' at /Users/hermespique/workspace/HanekeSwift/HanekeTests/Wrapper.swift:11:7
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: swift frontend command failed due to signal (use -v to see invocation)
Command /Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift failed with exit code 254
【问题讨论】：
这看起来像是一个错误的编译器错误...时间提交错误报告。玩通用代码时编译器很崩溃 尝试删除整个 init 函数和 isEqual 函数，看看它是否可以编译，然后将它们分别添加回去，如果没有它们编译，则查看哪个破坏了它。我注意到一些 Apple 类的子类化不会与生成的 init 一起编译，因此它很可能是一个将被修复的错误。 @KrisGellci 问题似乎是子类化 NSObject、使用泛型和具有变量的组合。不确定是否有解决方法。 这里有一个更简化的问题版本：class Wrapper<T> : NSObject let obj : T init(x : T) self.obj = x
我在这里注意到了一个类似的问题，但没有涉及 NSObject。此处注明：***.com/questions/24193957/…
【参考方案1】：
我找到了解决这个问题的方法
class Wrapper<T>
let _val: T[]
init(_ v: T)
_val = [v]
var val : T
get
return _val[0]
set
_val[0] = newValue
由于Array 是一个引用类型（即使它是结构），Wrapper 类的大小现在是固定的，编译器可以处理它。
【讨论】：
我很惊讶，现在 Swift 和 Xcode 6 已经发布，这仍然是必要的！ 我认为这行得通的原因是你不再继承 NSObject。 NSObject 子类不能有泛型。 @Jarsen 这也适用于NSObject 子类。
是的，用 Swift 1.2 测试过。【参考方案2】：
我认为这是一个带有泛型和 NSObject 的 X 代码错误
class Foo<T>:NSObject
let _foo:T?
init(foo:T)
_foo = foo
给出 swiftc 失败，退出代码为 254
删除 NSObject 工作正常。即：
class Foo<T>
let _foo:T?
init(foo:T)
_foo = foo
或者向泛型添加约束似乎有效。即：
class Foo<T:AnyObject>:NSObject
let _foo:T?
init(foo:T)
_foo = foo
【讨论】：
这里的第一个sn-p不再失败。【参考方案3】：我摆弄了你有趣的 (+1) sn-p 代码，这是我在避免编译器错误的同时能得到的最接近的代码：
struct Wrapper<T>
var obj : T
init(_ x : T)
obj = x
所以，如果你真的不需要 Wrapper 作为一个类，那么你就可以继续……直到 Xcode 的下一个版本；）
【讨论】：
【参考方案4】：在我看来，泛型不喜欢 NSObjects 类型，只喜欢 AnyObject 类型..
NSObject 不符合 AnyObject（它们在性质和功能上有所不同）.. 这意味着如果您需要创建泛型方法，则不能使用 Array 代替 NSArray。我认为这就是他们迅速离开 NSArray 的原因 .. 因为他们仍然有 NS .. 遗留的东西 .. 最重要的是 CoreData。我试图创建一个通用的 NSManagedObject 类来派生，它会使用这个强大的特性（泛型）。我做不到。
【讨论】：
【参考方案5】：这个小代码 sn-p（我的另一个 +1）仍然会导致 Xcode 7 beta 1 中的编译器崩溃，我猜它的意图是该代码不是有效的类定义。如果 Cupertino 的任何人收听此线程，我们将不胜感激提供礼貌的错误消息而不是崩溃。
我通过约束泛型参数实现NSObjectProtocol解决了这个问题
class Wrapper<T:NSObjectProtocol> : NSObject
let obj : T
init(x : T) self.obj = x
每当T 是NSManagedObject 的子类时，这对我构建与Wrapper<T> 匹配的函数时很有用。
【讨论】：
【参考方案6】：对于 Swift 2.0。此问题不再有效。
你可以有一个这样的类，编译器不会抱怨。
class Wrapper<T> : NSObject
let obj : T
init(x : T)
self.obj = x
【讨论】：
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