我在Swift（XCode beta 5）中使用泛型类和NSCoding遇到了麻烦。具体来说，此示例代码可以很好地工作：
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通用参数时；当我尝试编码对象时；我收到“无法识别的选择器发送到实例”错误：
class Foo<T> : 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<String>(bar: "hello, world")
NSKeyedArchiver.archiveRootObject(foo, toFile: "test.dat")
这是错误详细信息和堆栈跟踪：
[_TtC6SafeId14ArrayContainer00007F8893418E58 encodeWithCoder:]: unrecognized selector sent to instance 0x7f8890ee4080
2014-08-16 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
在我阅读本文时，当类为通用类时，Swift无法调用encodeWithCoder的实现。这样对吗 ？如何在通用类上使用NSCoding来解决此问题？
使类成为通用类之后，它就与Objective-C不兼容。NSCoder的所有内容都发生在无法访问您的类的Objective-C中。
请注意，使类通用也有其他后果。例如，如果要添加描述属性，则还会出现编译时错误：
// Error: '@objc' getter for non-'@objc' property
override var description: String {
return "Foo: \(bar)"
}
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我来说两句