private(set) internal var config: Int = 0

http://stackoverflow.com/a/25720651/3548428

没有初始值就是可选

初始化时一定有值，是 隐性可选
初始化时不一定有值，是 显性可选

Set the repeatCount to Float.infinity. This compiles and works.

In all probability, HUGE_VALF was a legacy value in any case.

Still, it's a bit of a surprise that these numeric constant names are not seen by Swift. I did try importing in the bridging header but it didn't help.

参考 http://stackoverflow.com/a/24343909/3548428

http://nshipster.cn/guard-and-defer/

http://www.jianshu.com/p/eb718439551f

class Classy {

    var foo: Int! { didSet { doStuff() } }

    init( foo: Int ) {
        // closure invokes didSet
        ({ self.foo = foo })()
    }

}

参考 http://stackoverflow.com/a/29501998/3548428

class SomeClass {
    var someProperty: AnyObject! {
        didSet {
            //do some Stuff
        }
    }

    init(someProperty: AnyObject) {
        setSomeProperty(someProperty)
    }

    func setSomeProperty(newValue:AnyObject) {
        self.someProperty = newValue
    }
}

参考 http://stackoverflow.com/a/25231068/3548428

public class MyNewType : NSObject {
    public var myRequiredField:Int
    public var myOptionalField:Float? {
        willSet {
            if let newValue = newValue {
                print("I'm going to change to \(newValue)")
            }
        }
        didSet {
            if let myOptionalField = self.myOptionalField {
                print("Now I'm \(myOptionalField)")
            }
        }
    }

    override public init() {
        self.myRequiredField = 1

        super.init()

        // Non-defered
        self.myOptionalField = 6.28

        // Defered
        defer {
            self.myOptionalField = 3.14
        }
    }
}

参考 http://stackoverflow.com/a/33979852/3548428

参考

http://coderforart.com/mweb-medium-like-theme.html