CS193P 5. Objective-C Compatibility, Proper

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1. Objective-C 兼容性

Bridging

Swift 可以无缝使用以前 Objective-C 的 API，但是一些特殊的数据类型需要桥接。桥接是指可以互换的使用。

NSString <-> String

NSArray <-> Array

NSDictionary <-> Dictionary<NSObject, AnyObject>

Int, Float, Double, Bool -> NSNumber (反之不行)

99%的桥接均是隐式完成的。

2. 属性列表

属性列表指 AnyObject 是一下六种类型的集合列表：
NSString, NSArray, NSDictionary, NSNumber, NSData, NSDate。

处理属性列表通常需要映射：如 is 和 as。

属性列表可以“盲”传递数据，也可以作为一种通用数据结构-类似泛型。

NSUserDefaults 作为一种使用属性列表的存储机制。本质上就是一个小的存储数据列表的数据库。通常用存储“设置”信息。
NSUserDefaults 可以通过名称或键来存储或检索整个属性列表。

以下用法摘自：NSUserDefaults — A Swift Introduction

存储 NSUserDefaults

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let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject("Coding Explorer", forKey: "userNameKey")

NSUserDefaults 常用的写入方法:

  • func setBool(value: Bool, forKey defaultName: String)
  • func setInteger(value: Int, forKey defaultName: String)
  • func setFloat(value: Float, forKey defaultName: String)
  • func setDouble(value: Double, forKey defaultName: String)
  • func setObject(value: AnyObject?, forKey defaultName: String)
  • func setURL(url: NSURL, forKey defaultName: String)

iOS 8或更新版本不要使用 synchronize。

读取 NSUserDefaults

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let defaults = NSUserDefaults.standardUserDefaults()
if let name = defaults.stringForKey("userNameKey")
{
    println(name)
}

对应的常用读取 NSUserDefaults 的方法：

  • func boolForKey(defaultName: String) -> Bool
  • func integerForKey(defaultName: String) -> Int
  • func floatForKey(defaultName: String) -> Float
  • func doubleForKey(defaultName: String) -> Double
  • func objectForKey(defaultName: String) -> AnyObject?
  • func URLForKey(defaultName: String) -> NSURL?
  • func dataForKey(defaultName: String) -> NSData?
  • func stringForKey(defaultName: String) -> String?
  • func stringArrayForKey(defaultName: String) -> [AnyObject]?
  • func arrayForKey(defaultName: String) -> [AnyObject]?
  • func dictionaryForKey(defaultName: String) -> [NSObject : AnyObject]?

使用常量做键

方便在一处修改，容易理解编译报错。

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let userNameKeyConstant = "userNameKey"

@IBAction func writeButton(sender: UIButton)
{
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.setObject("Coding Explorer", forKey: userNameKeyConstant)
}

@IBAction func readButton(sender: UIButton)
{
    let defaults = NSUserDefaults.standardUserDefaults()
    if let name = defaults.stringForKey(userNameKeyConstant)
    {
        print(name)
    }
}

3. 视图

视图代表了一个长方形区域。

视图是等级，类似单继承：一个视图只可以有一个 superview，但可以有很多 subviews。

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//
//  FaceView.swift
//  Happiness
//
//  Created by Will Ge on 7/17/15.
//  Copyright © 2015 gewill.org. All rights reserved.
//

import UIKit

class FaceView: UIView {
    
    var lineWidth: CGFloat = 5 { didSet { setNeedsDisplay() } }
    var color: UIColor = UIColor.blueColor() { didSet { setNeedsDisplay() } }
    var scale: CGFloat = 0.9
    var faceCenter: CGPoint {
        return convertPoint(center, fromView: superview)
    }
    
    var faceRadius: CGFloat {
        return min(bounds.size.width, bounds.size.height) / 2 * scale
    }
    
    // 覆写 drawRect，自定义视图
    override func drawRect(rect: CGRect) {
        
        // 画脸
        let facePath = UIBezierPath(arcCenter: faceCenter, radius: faceRadius, startAngle: 0, endAngle: CGFloat(2 * M_PI), clockwise: true)
        facePath.lineWidth = lineWidth
        color.set()
        facePath.stroke()
        
        // 画眼
        bezierPathForEye(.Left).stroke()
        bezierPathForEye(.Right).stroke()
        
        // 画嘴巴
        let smiliness = 0.8
        let smilePath = bezierPathForSmile(smiliness)
        smilePath.stroke()
    }
    
    
    private struct Scaling {
        static let FaceRadiusToEyeRadiusRatio: CGFloat = 10
        static let FaceRadiusToEyeOffsetRatio: CGFloat = 3
        static let FaceRadiusToEyeSeparationRatio: CGFloat = 1.5
        static let FaceRadiusToMouthWidthRatio: CGFloat = 1
        static let FaceRadiusToMouthHeightRatio: CGFloat = 3
        static let FaceRadiusToMouthOffsetRatio: CGFloat = 3
        
    }
    
    // 定义枚举：左右眼
    private enum Eye { case Left, Right }
    
    // 定义函数：眼睛的路径
    private func bezierPathForEye(whichEye: Eye) -> UIBezierPath {
        
        let eyeRadius = faceRadius / Scaling.FaceRadiusToEyeRadiusRatio
        let eyeVerticalOffset = faceRadius / Scaling.FaceRadiusToEyeOffsetRatio
        let eyeHorizontalSeparation = faceRadius / Scaling.FaceRadiusToEyeSeparationRatio
        
        var eyeCenter = faceCenter
        eyeCenter.y -= eyeVerticalOffset
        switch whichEye {
        case .Left: eyeCenter.x -= eyeHorizontalSeparation / 2
        case .Right: eyeCenter.x += eyeHorizontalSeparation / 2
        }
        
        let path = UIBezierPath(arcCenter: eyeCenter, radius: eyeRadius, startAngle: 0, endAngle: CGFloat(2 * M_PI), clockwise: true)
        path.lineWidth = lineWidth
        return path
        
    }
    
    // 定义函数：嘴巴的路径
    private func bezierPathForSmile(fractionOfMaxSmile: Double) -> UIBezierPath {
        
        let mouthWidth = faceRadius / Scaling.FaceRadiusToMouthWidthRatio
        let mouthHeight = faceRadius / Scaling.FaceRadiusToMouthHeightRatio
        let mouthVerticalOffset = faceRadius / Scaling.FaceRadiusToMouthOffsetRatio
        
        let smileHeight = CGFloat(max(min(fractionOfMaxSmile, 1), -1)) * mouthHeight
        
        let start = CGPoint(x: faceCenter.x - mouthWidth / 2, y: faceCenter.y + mouthVerticalOffset)
        let end = CGPoint(x: start.x + mouthWidth, y: start.y)
        let cp1 = CGPoint(x: start.x + mouthWidth / 3, y: start.y + smileHeight)
        let cp2 = CGPoint(x: end.x - mouthWidth / 3, y: cp1.y)
        
        let path = UIBezierPath()
        path.moveToPoint(start)
        path.addCurveToPoint(end, controlPoint1: cp1, controlPoint2: cp2)
        path.lineWidth = lineWidth
        return path
    }

    
}