我如何在 Swift 中声明 typedef

Question

如果我需要在 Swift 中使用自定义类型，我可以typedef ，我该怎么做？ （类似于闭包语法 typedef）

Answer 1

关键字typealias用于代替typedef ：

typealias CustomType = String
var customString: CustomType = "Test String"

Answer 2

添加到上面的答案中：

"typealias" 是使用的关键字 is swift，它的功能与 typedef 类似。

    /*defines a block that has 
     no input param and with 
     void return and the type is given 
     the name voidInputVoidReturnBlock*/        
    typealias voidInputVoidReturnBlock = () -> Void

    var blockVariable :voidInputVoidReturnBlock = {

       println(" this is a block that has no input param and with void return")

    } 

要使用输入参数创建 typedef，语法如下所示：

    /*defines a block that has 
     input params NSString, NSError!
    and with void return and the type 
    is given the name completionBlockType*/ 
    typealias completionBlockType = (NSString, NSError!) ->Void

    var test:completionBlockType = {(string:NSString, error:NSError!) ->Void in
        println("\(string)")

    }
    test("helloooooooo test",nil);
    /*OUTPUTS "helloooooooo test" IN CONSOLE */