swift 闭包

例子1：

使用sort函数

let names = ["A-a","C","B-b","D"]
let reversed = names.sort(backwards)
func backwards(firstStr: String,secondStr: String) -> Bool {
        return firstStr < secondStr;
    }

例子2：

自定义对象

class Model {
    var name = String();
    var age = String();
    
    init(name: String,age: String){
        self.name = name;
        self.age = age;
    };
    
    
}

let models =   [Model.init(name: "A-a",age: "12"),Model.init(name: "D",age: "11"),Model.init(name: "B-b",age: "21"),Model.init(name: "C-c",age: "19")]
        let nameResult = models.sort { (ml1,ml2) -> Bool in
            return ml1.name < ml2.name;
        }
        
        for ml in nameResult {
            print(ml.name,ml.age);
        }
        
        
        print("------------------")
        
        let ageResult = models.sort { $0.age < $1.age }

        for ml in ageResult {
            print(ml.age,ml.name);
        }

输出：

A-a 12
B-b 21
C-c 19
D 11
------------------
11 D
12 A-a
19 C-c
21 B-b

参考：http://www.jianshu.com/p/ad71c94e7bc6