Swift:可选值中的可选文本

Question

如何在不强制 ! 的情况下删除可选值上的 Optional("") 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 value
var url = "\(self.session?.apiURL)/api/products.json"

// private session
private 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 session 有一个值时，url 有一个值:

Optional("my_api_url_here")/api/products.json

Answer 1

您可以使用这个 pod http://cocoapods.org/pods/NoOptionalInterpolation .

或者，将此代码添加到您的项目以删除字符串插值中的 Optional(...) 和 nil 文本:

public protocol Unwrappable {
    func unwrap() -> Any?
}

extension Optional: Unwrappable {
    public func unwrap() -> Any? {
        switch self {
        case .None:
            return nil
        case .Some(let unwrappable as Unwrappable):
            return unwrappable.unwrap()
        case .Some (let some):
            return some
        }
    }
}

public extension String {
    init(stringInterpolationSegment expr: Unwrappable) {
        self = String(expr.unwrap() ?? "")
    }
}

请注意，简单地覆盖 Optional 的 description 函数将不适用于字符串插值，尽管它适用于 print。