{ (parameters/接收的參數(shù)) -> (return type/閉包返回值類型) in
  statements/保存在閉包中需要執(zhí)行的代碼
 }

//為沒有參數(shù)也沒有返回值的閉包類型起一個別名
 typealias Nothing = () -> ()

 //如果閉包的沒有返回值，那么我們還可以這樣寫，
 typealias Anything = () -> Void

 //為接受一個Int類型的參數(shù)不返回任何值的閉包類型 定義一個別名：PrintNumber
 typealias PrintNumber = (Int) -> ()

 //為接受兩個Int類型的參數(shù)并且返回一個Int類型的值的閉包類型 定義一個別名：Add
 typealias Add = (Int, Int) -> (Int)

//為(_ num1: Int, _ num2: Int) -> (Int) 類型的閉包定義別名：Add
 typealias Add = (_ num1: Int, _ num2: Int) -> (Int)
//創(chuàng)建一個 Add 類型的閉包常量：addCloser1
 let addCloser1: Add
//為已經(jīng)創(chuàng)建好的常量 addCloser1 賦值
 addCloser1 = {
  (_ num1: Int, _ num2: Int) -> (Int) in
  return num1 + num2
 }
//調(diào)用閉包并接受返回值
 let result = addCloser1(20, 10)

//創(chuàng)建一個 (_ num1: Int, _ num2: Int) -> (Int) 類型的閉包常量：addCloser1
 let addCloser1: (_ num1: Int, _ num2: Int) -> (Int)
//為已經(jīng)創(chuàng)建好的常量 addCloser1 賦值
 addCloser1 = {
   (_ num1: Int, _ num2: Int) -> (Int) in
   return num1 + num2
 }
 //調(diào)用閉包并接受返回值
 let result = addCloser1(20, 10)

//創(chuàng)建一個 (Int, Int) -> (Int) 類型的閉包常量：addCloser1
 let addCloser1: (Int, Int) -> (Int)
//為已經(jīng)創(chuàng)建好的常量 addCloser1 賦值
 addCloser1 = {
   (num1, num2) in
   return num1 + num2
 }
//調(diào)用閉包并接受返回值
 let result = addCloser1(20, 10)

//創(chuàng)建一個 (Int, Int) -> (Int) 類型的閉包常量：addCloser1 并賦值
 let addCloser1: (Int, Int) -> (Int) = {
   (num1, num2) in
   return num1 + num2
  } 
//調(diào)用閉包并接受返回值
 let result = addCloser1(20, 10)

//創(chuàng)建一個 () -> (String) 類型的閉包常量：addCloser1 并賦值
  let addCloser1: () -> (String) = {
   return "這個閉包沒有參數(shù)，但是有返回值"
   }
 //調(diào)用閉包并接受返回值
  let result = addCloser1()

//創(chuàng)建一個 (String, String) -> (String) 類型的閉包常量：addCloser1 并賦值
  let addCloser1: (String, String) -> (String) = {
   return "閉包的返回值是:\($0),\($1)"
   }
 //調(diào)用閉包并接受返回值
  let result = addCloser1("Hello", "Swift!")

import UIKit
class SecondViewController: UIViewController {
 //輸入文本框
 @IBOutlet weak var textField: UITextField!
 //為創(chuàng)建一個(String) -> () 的可選類型的閉包變量作為控制器的屬性
 var closer: ((String) -> ())?
 //返回按鈕的點擊事件
 @IBAction func backButtonDidClick(_ sender: AnyObject) {
  //首先判斷closer閉包是否已經(jīng)被賦值，如果已經(jīng)有值，直接調(diào)用該閉包，并將輸入的文字傳進去。
  if closer != nil {
   closer!(textField.text!)
  }
  navigationController?.popViewController(animated: true)
 }
}

import UIKit
class FirstViewController: UIViewController {
 //顯示文字的label
 @IBOutlet weak var label: UILabel!
 //重寫這個方法
 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  //拿到跳轉(zhuǎn)的目標控制器
  let secondVC = segue.destination as! SecondViewController
  //為目標控制器的閉包屬性賦值
  secondVC.closer = {
   //將閉包的參數(shù)(輸入的文本內(nèi)容)顯示在label上
   self.label.text = $0
  }
 }
}

//為接受一個Int類型的參數(shù)并且返回一個Int類型的值的閉包類型定義一個別名：Number
 typealias Number = (num1: Int) -> (Int)
 //定義一個接收Number類型的參數(shù)沒有返回值的方法
 func Text(num: Number) {
  //code
 }

//拼接兩個字符串和一個整數(shù)
 func combine(handle:(String, String) -> (Void), num: Int) {
   handle("hello", "world \(num)")
  }
//方法調(diào)用
 combine(handle: { (text, text1) -> (Void) in
   print("\(text) \(text1)")
   }, num: 2016)

 func combine1(num:Int, handle:(String, String)->(Void)) {
   handle("hello", "world \(num)")
 }
 combine1(num: 2016) { (text, text1) -> (Void) in
   print("\(text) \(text1)")
 }

 func combine2(handle:(String, String)->(Void)) {
   handle("hello", "world")
 }
 combine2 { (text, text1) -> (Void) in
   print("\(text) \(text1)")
 }

func request(methodType:RequestMethodType, urlString: String, parameters: [String : AnyObject], completed: @escaping (AnyObject?, NSError?) -> ()) {
  // 1.封裝成功的回調(diào)
  let successCallBack = { (task : URLSessionDataTask?, result : Any?) -> Void in
   completed(result as AnyObject?, nil)
  }
  // 2.封裝失敗的回調(diào)
  let failureCallBack = { (task : URLSessionDataTask?, error : Error?) -> Void in
   completed(nil, error as NSError?)
  }
  //判斷是哪種請求方式
  if methodType == .get {
   get(urlString, parameters: parameters, success: successCallBack, failure: failureCallBack)
  } else {
   post(urlString, parameters: parameters, success: successCallBack, failure: failureCallBack)
  }
 }

import UIKit
class ThirdViewController: UIViewController {
 var callBack: ((String) -> ())?
 override func viewDidLoad() {
  super.viewDidLoad()
  printString { (text) in
   print(text)
   //閉包中捕獲了self
   self.view.backgroundColor = UIColor.red
  }
 }
 func printString(callBack:@escaping (String) -> ()) {
  callBack("這個閉包返回一段文字")
  //控制器強引用于著callBack
  self.callBack = callBack
 }
 deinit {
  print("ThirdViewController---釋放了")
 }
}

import UIKit
class ThirdViewController: UIViewController {
 var callBack: ((String) -> ())?
 override func viewDidLoad() {
  super.viewDidLoad()
  //將self申明為弱引用類型，打破循環(huán)引用
  weak var weakSelf = self
  printString { (text) in
   print(text)
   //閉包中鋪捕獲了self
   weakSelf?.view.backgroundColor = UIColor.red
  }
 }
 func printString(callBack:@escaping (String) -> ()) {
  callBack("這個閉包返回一段文字")
  //控制器強引用于著callBack
  self.callBack = callBack
 }
 deinit {
  print("ThirdViewController---釋放了")
 }
}

import UIKit
class ThirdViewController: UIViewController {
  var callBack: ((String) -> ())?
  override func viewDidLoad() {
    super.viewDidLoad()
    printString {[weak self] (text) in
      print(text)
      self?.view.backgroundColor = UIColor.red
    }
  }
  func printString(callBack:@escaping (String) -> ()) {
    callBack("這個閉包返回一段文字")
    //控制器強引用于著callBack
    self.callBack = callBack
  }
  deinit {
    print("ThirdViewController---釋放了")
  }
}

import UIKit
class ThirdViewController: UIViewController {
  var callBack: ((String) -> ())?
  override func viewDidLoad() {
    super.viewDidLoad()
    printString {[unowned self] (text) in
      print(text)
      self?.view.backgroundColor = UIColor.red
    }
  }
  func printString(callBack:@escaping (String) -> ()) {
    callBack("這個閉包返回一段文字")
    //控制器強引用于著callBack
    self.callBack = callBack
  }
  deinit {
    print("ThirdViewController---釋放了")
  }
}