Swift 2.0元组模式元素标签必须是'_'

Question

我一直在尝试修复自swift 2.0更新以来的所有代码。我有这似乎是现在的方式的元组工作的一个问题：

public func generate() -> AnyGenerator <(String, JSON)> { 
    switch self.type { 
    case .Array: 
     let array_ = object as! [AnyObject] 
     var generate_ = array_.generate() 
     var index_: Int = 0 
     return anyGenerator{ 
      if let element_: AnyObject = generate_.next() { 
       return ("\(index_++)", JSON(element_)) 
      } else { 
       return nil 
      } 
     } 
    case .Dictionary: 
     let dictionary_ = object as! [String : AnyObject] 
     var generate_ = dictionary_.generate() 
     return anyGenerator{ 
      if let (key_: String, value_: AnyObject) = generate_.next() { 
       return (key_, JSON(value_)) 
      } else { 
       return nil 
      } 
     } 
    default: 
     return anyGenerator{ 
      return nil 
     } 
    } 
} 

具体线路：

if let (key_: String, value_: AnyObject) = generate_.next() 

抛出错误：元组模式元素标签“键”必须“_”

我试图让这个变化已经，但我没有工作...

任何想法？

Answer 1

问题是：我们不能使用类型注释里面的元组模式了。

在release notes：

Type annotations are no longer allowed in patterns and are considered part of the outlying declaration. This means that code previously written as:

var (a : Int, b : Float) = foo() 

needs to be written as:

var (a,b) : (Int, Float) = foo() 

if an explicit type annotation is needed. The former syntax was ambiguous with tuple element labels. (20167393)

所以，你可以：

if let (key_, value_): (String, AnyObject) = generate_.next() { 

但在这种情况下，你可以省略: (String, AnyObject)：

if let (key_, value_) = generate_.next() {