斯坦福Developing iOS 8 Apps学习笔记（二）

一些storyboard的trick

@IBDesignable 可以在storyboard中预览代码绘图效果（有点tricky，如果画不出来也是有可能的（绘图依赖某些复杂依赖关系））

@IBInspectable 让某些变量的设置可以在Storyboard中进行，类似于storyboard中原生的Attribute aspect

Extensions

对于新手来说，Extension主要功能在于

增加某些辅助功能，辅助函数

注意

在extension中overwrite是不行的

定义property只能是computed，不能有storage

对于大神来说Extension是一种架构的方式，具体可在架构书中学习

Protocols and Delegation

Protocol书写中需要注意的地方

protocol SomeProtocol:(class), InheritedProtocol {
var property:Int {get,set}
func aMethod(arg1:Double, ...) -> SomeType
mutating func change()
init(arg:Type)
}

class表示只有类可以遵守的协议

property要标明get,set还是get

对于在结构体和枚举中使用的协议，如果要修改property，需要标注 mutating

Delegation思想的使用方法

Create a delegation protocol(defines what the View wants the Controller to take care of)

Create a delegate property in the View whose type is that delegation protocol

Use the delegation property in the View to get/do

Controller declares that it implements the protocol things it can’t own or control

Controllers set self as the delegation of the View

??运算符

expression1 ?? expression2

相当于

if expression1 = nil

return expression2

else

return expression1

Gestures

UIPanGestureRecognizer

translationInView(view:UIView) -> CGPoint

velocityInView(view:UIView) -> CGPoint

setTranslation(translation:CGPoint, inView:UIView)

state:UIGestureRecognizerState

.Possible

.Recognized(discrete)

(continues) .Begin .Changed .Ended

.Failed

.Cancelled(Phone call in)

对于state的处理

switch gesture.state
case .Changed:fallthrough
case .Ended:
let translation = gesture.translationInView(aView)
//update
gesture.setTranslation(CGPointZero,inView:aView)
default:break

UIPinchGestureRecognizer

var scale:CGFloat

var velocity:CGFloat{get}

UIRotationGestureRecognizer

var rotation:CGFloat //in radians

var velocity:CGFloat{get} //in radians

UISwipeGestureRecognizer

var direction(set when init):UISwipeGestureRecognizerDirection

var numberOfTouchesRequired:Int //finger count

观察state .Recognized状态

UITapGestureRecognizer

var numberOfTapsRequired:Int //点击次数 If Double,check out .Ended

var numberOfTouchesRequired:Int //Finger Count