Swift：可选值中的可选文本

概述如何在不强制显示的情况下显示可选值上的可选(“”)文本. 更新 // I have somthing like this declared outside class// I put question mark wrapper since I don't know when this session might have a valuevar url = "\(self.session?.ap 如何在不强制显示的情况下显示可选值上的可选(“”)文本.

更新

// I have somthing like this declared outsIDe class// I put question mark wrapper since I don't kNow when this session might have a valuevar url = "\(self.session?.APIURL)/API/products.Json"// private sessionprivate var _session:Session?class MyClass{   .   .   .   // the value of APIURL depends on session,session has optional value and declared as   // custom lazy loaded var session   var session:Session?   {      get      {           if _session == nil          {           _session = // fetch from coredata store if there is an active session. Might return nil           // if no active session           if _session == nil           {              // I just print "No active session"           }         }         // return _session may or may not contain any value         return _session      }   }}

当会话具有值时,url具有值：

Optional("my_API_url_here")/API/products.Json

您可以使用 ？？ (null coalescing operator)打开它并提供默认值(如果它是nil)

let sessionAPIURL = self.session?.APIURL ?? ""var url = "\(sessionAPIURL)/API/products.Json"

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