class Foo : NSObject,NSCoding{ let bar: String init(bar: String){ self.bar = bar; } func encodeWithCoder(aCoder: NSCoder!){ aCoder.encodeObject(bar,forKey: "bar") } required init(coder aDecoder: NSCoder!){ self.bar = aDecoder.decodeObjectForKey("bar") as String super.init() }}let foo = Foo(bar: "hello,world")NSKeyedArchiver.archiveRootObject(foo,tofile: "test.dat")
但是,当我尝试相同的代码,并添加一个泛型参数;当我尝试编码对象;我收到一个’无法识别的选择器发送到实例’错误:
class Foo<T> : NSObject,forKey: "bar") } required init(coder aDecoder: NSCoder!){ self.bar = aDecoder.decodeObjectForKey("bar") as String super.init() }}let foo = Foo<String>(bar: "hello,tofile: "test.dat")
以下是错误详细信息和堆栈跟踪:
[_TtC6SafeID14ArrayContainer00007F8893418E58 encodeWithCoder:]: unrecognized selector sent to instance 0x7f8890ee40802014-08-16 10:43:54.632 SafeID[1778:32501] *** Terminating app due to uncaught exception 'NSinvalidargumentexception',reason: '-[_TtC6SafeID14ArrayContainer00007F8893418E58 encodeWithCoder:]: unrecognized selector sent to instance 0x7f8890ee4080'*** First throw call stack:( 0 CoreFoundation 0x0000000103a6e3e5 __exceptionPreprocess + 165 1 libobjc.A.dylib 0x000000010371e967 objc_exception_throw + 45 2 CoreFoundation 0x0000000103a754fd -[NSObject(NSObject) doesNotRecognizeSelector:] + 205 3 CoreFoundation 0x00000001039cd5ff ___forwarding___ + 495 4 CoreFoundation 0x00000001039cd388 _CF_forwarding_prep_0 + 120 5 Foundation 0x00000001032eaa75 _encodeObject + 1120 6 Foundation 0x0000000103326bf5 +[NSKeyedArchiver archiveRootObject:tofile:] + 241
当我读到这一点,当类是通用的时,Swift无法调用encodeWithCoder的实现.它是否正确 ?为了在泛型类上使用NSCoding,我该如何解决这个问题?
当您将类泛型化时,它变得与Objective-C不兼容. NSCoder的东西都发生在不能再访问你的类的Objective-C中.注意还有其他的后果,使类通用.例如,如果要添加描述属性,则还会收到编译时错误:
// Error: '@objc' getter for non-'@objc' propertyoverrIDe var description: String { return "Foo: \(bar)"}总结
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