我想创建一个不限制键类型的字典(如NSDictionary)
所以我试过
var dict = Dictionary<Any,Int>()
和
var dict = Dictionary<AnyObject,Int>()
结果
error: type 'Any' does not conform to protocol 'Hashable' var dict = Dictionary<Any,Int>() ^ <REPL>:5:12: error: cannot convert the expression's type '<<error type>>' to type '$T1' var dict = Dictionary<Any,Int>() ^~~~~~~~~~~~~~~~~~~~~~
OK,我将使用Hashable
var dict = Dictionary<Hashable,Int>()
但
error: type 'Hashable' does not conform to protocol 'Equatable' var dict = Dictionary<Hashable,Int>() ^ Swift.Equatable:2:8: note: '==' requirement refers to 'Self' type func ==(lhs: Self,rhs: Self) -> Bool ^ Swift.Hashable:1:10: note: type 'Hashable' does not conform to inherited protocol 'Equatable.Protocol' protocol Hashable : Equatable ^ <REPL>:5:12: error: cannot convert the expression's type '<<error type>>' to type '$T1' var dict = Dictionary<Hashable,Int>() ^~~~~~~~~~~~~~~~~~~~~~~~~~~
所以Hashable继承自Equatable,但它不符合Equatable ???我不明白…
反正,不断尝试
typealias KeyType = protocol<Hashable,Equatable> // KeyType is both Hashable and Equatable var dict = Dictionary<KeyType,Int>() // now you happy?
没有运气
error: type 'KeyType' does not conform to protocol 'Equatable' var dict = Dictionary<KeyType,rhs: Self) -> Bool ^ Swift.Hashable:1:10: note: type 'KeyType' does not conform to inherited protocol 'Equatable.Protocol' protocol Hashable : Equatable ^ <REPL>:6:12: error: cannot convert the expression's type '<<error type>>' to type '$T1' var dict = Dictionary<KeyType,Int>() ^~~~~~~~~~~~~~~~~~~~~~~~~~
我现在这么迷路,我怎么能让编译器满意我的代码?
我想使用字典
var dict = Dictionary<Any,Int>() dict[1] = 2 dict["key"] = 3 dict[SomeEnum.SomeValue] = 4
我知道我可以使用Dictionary< NSObject,Int>,但它不是我真正想要的。
我相信,从Swift 1.2,你可以使用ObjectIdentifier结构体。它实现了Hashable(因此Equatable)以及Comparable。您可以使用它来包装任何类实例。我猜测的实现使用包装对象的底层地址为hashValue,以及在==运算符内。
原文链接:/swift/321200.html