Swift ThenSwift 初始化語法糖

Then 是實(shí)現(xiàn) Swift 對象初始化的一個語法糖

初始化 UILabel 并設(shè)置其屬性

let label = UILabel().then {
  $0.textAlignment = .center
  $0.textColor = .black
  $0.text = "Hello, World!"
}

相當(dāng)于：

let label: UILabel = {
  let label = UILabel()
  label.textAlignment = .center
  label.textColor = .black
  label.text = "Hello, World!"
  return label
}()

技巧

• 在所有的 NSObject 子類中使用 then() 

  let queue = OperationQueue().then {
    $0.maxConcurrentOperationCount = 1
  }

• 在自定義類中使用，只需進(jìn)行簡單擴(kuò)展：

  extension MyType: Then {}
  
  let instance = MyType().then {
    $0.really = "awesome!"
  }

• 拷貝值類型數(shù)據(jù)時候 with() 

  let newFrame = oldFrame.with {
    $0.size.width = 200
    $0.size.height = 100
  }
  newFrame.width // 200
  newFrame.height // 100

• 使用 do() 減少類型處理

  UserDefaults.standard.do {
    $0.set("devxoul", forKey: "username")
    $0.set("[email protected]", forKey: "email")
    $0.synchronize()
  }

真實(shí)示例：

final class MyViewController: UIViewController {

  let titleLabel = UILabel().then {
    $0.textColor = .black
    $0.textAlignment = .center
  }

  let tableView = UITableView().then {
    $0.backgroundColor = .clear
    $0.separatorStyle = .none
    $0.register(MyCell.self, forCellReuseIdentifier: "myCell")
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    self.view.addSubview(self.titleLabel)
    self.view.addSubview(self.tableView)
  }

}

安裝

• For iOS 8+ projects with CocoaPods:

  pod 'Then'

• For iOS 8+ projects with Carthage:

  github "devxoul/Then"
  

• Using Swift Package Manager:

  import PackageDescription
  
  let package = Package(
    name: "MyAwesomeApp",
    dependencies: [
      .Package(url: "https://github.com/devxoul/Then", majorVersion: 2),
    ]
  )