如何在Swift中声明类型定义

If I require a custom type in Swift, that I could typedef, how do I do it? (Something like a closure syntax typedef)

如果我需要一个Swift自定义类型，我可以用typedef，我该怎么做呢?(类似于闭包语法typedef)

2 个解决方案

#1

107

The keyword typealias is used in place of typedef

关键字typealias被用来代替typedef

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

#2

added to the answer above:

加上上面的答案:

"typealias" is the keyword used is swift which does similar function as typedef.

“typealias”是使用的关键字是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")

    }

To create a typedef with input param the syntax is as shown below :

要使用输入参数创建类型定义，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 */

#1

107