当我实现Hashable协议(protocol)时。需要在类外部定义一个可等式的协议(protocol)函数，如下所示。如下。func==(lhs:Swap,rhs:Swap)->Bool{return(lhs.cookieA==rhs.cookieA&&lhs.cookieB==rhs.cookieB)||(lhs.cookieB==rhs.cookieA&&lhs.cookieA==rhs.cookieB)}classSwap:Printable,Hashable{varcookieA:CookievarcookieB:Cookieinit(cookieA:Cookie,cooki