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Swift 千金方 2 - Stanford CS193p 学习笔记

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大名鼎鼎的经典 iOS 开发教程。我在 iOS 9.2, Swift 2.1 和 Xcode 7 上重写了一次（课程默认是 iOS8 以及旧版本的 Swift，会有些不同），项目代码在这里

总体来说课程非常规范，但是因为时间所限没有办法覆盖到方方面面，比方说如何测试一个 app，如何优化 app 的性能等等。最好自己学过 Swift，以及对于函数式编程，闭包等有一定的了解。

我当前的开发环境

  • Xcode 7.2
  • OS X 10.11.2
  • Swift 2.1
  • iOS 9.2 (iPhone 6s, iPod Touch 6th, iPad 3)

1 Logistics, iOS 8 Overview

What’s in iOS

  • Cocoa Touch

    • Multi-Touch, Alerts, Core Motion, Web View, View Hierarchy, Map Kit, Localization, Image Picker, Controls, Camera

  • Media

    • Core Audio, JPEG/PNG/TIFF, OpenAL, PDF, Audio Mixing, Quartz(2D), Audio Recording, Core Animation, Video Playback, OpenGL ES

  • Core Services

    • Collections, Core Location, Address Book, Net Services, Networking, Threading, File Access, Preferences, SQLite, URL Utilities

  • Core OS

    • OSX kernel, Power Management, Mach 3.0, Keychain Access, BSD, Certificates, Sockets, File System, Security, Bonjour

Platform Components

  • Tools

    • Xcode 6 (Latest is 7)

  • Language(s)

    • Swift, Modern Language
    • let value = formatter.numberFromString(display.text!)?.doubleValue

  • Frameworks

    • Foundation, Core Data, UIKit, Core Motion, Map Kit

  • Design Strategy

    • MVC

Calculator Tutorial

  • Organization Identifier 是你的身份验证，需要保证独立性

  • 尽可能把控件放到蓝线上，也就意味着某种对齐

  • weak 关键字，与 reference counting 相关，具体后面会说

  • 对象都在 heap 中存在

  • 能用 let 尽量用 let，增加可读性

  • option(alt) 点击变量可以查看帮助

  • optional 类型，可能是当前类型的值，或者是 nil，例如 String?

    • nil 就是 not set

  • 在 optional 类型后面加 ! 可以取出对应的值，但如果原来值是 nil，就会崩溃

  • 所有的变量都必须被初始化

2 More Xcode and Swift, MVC

  • 为什么 UILabel 之类的 outlet 可以直接声明 ! 而不需要像之前所说的那样所有变量都必须被初始化呢？因为作为控件变量称为 implicit unwrap，走 storyboard 另外的机制
  • 右键点击一个控件会显示当前和该控件绑定的事件，可以在这里操作进行绑定和解绑定
  • 新建数组 var operandStack = Array<Double>()，可以被 infer 的类型最好就不要明写出来
  • 变量的 set get 中有神奇变量 newValue
  • command + / 可以快速注释
  • 利用 Swift 本身的特性可以写出非常精简的代码
  • 之后是 MVC 的介绍

3 Applying MVC

  • 新建一个 class：File -> New -> File -> Swift File
  • 虽然没有要求类名和文件名一致，但是最好还是一样，这样比较符合惯例
  • 理论上来说不应该在一个 Model 类中 import UIkit
  • 可以用快捷语法来生成数组 [TypeName]()
  • 可以用快捷语法来生成字典 [KeyType: ValueType]()
  • *, +, sqrt 这些内置函数可以直接当参数传
  • 在字典里返回的是 optional 类型
  • 传参时除非传的是 class，不然都是传入一个复制的值
  • 传值的时候参数隐含是 let 的，即不可变
  • 函数可以直接返回一个 tuple
  • option(alt) 加点击文件可以把文件放到另一边
  • if let xxx = xxx {} 是通常的处理 optional 类型的方式
  • switch 如果列举了所有情况就不需要 default: break
  • private enum Op: CustomStringConvertible 由 Printable 更名而来

4 More Swift and Foundation Frameworks

不是所有的都记录，只挑了一些我觉得和之前学的语言差异比较大的，很多内容在我之前的学习笔记里都有覆盖

Optional

An Optional is just an enum

enum Optional<T>{
	case None
	case Some(T)
}
let x: String? = nil
// is
let x = Optional<String>.None

let x: String? = "hello"
// is
let x = Optional<String>.Some("hello")

var y = x!
// is
switch x {
	case Some(let value): y = value
	case None: // raise an exception
}

Other Classes

  • NSObject

    • Base class for all objective-C classes. Some advanced features will require you to subclass from NSObject

  • NSNumber

    • Generic number-holding class

  • NSDate

    • Used to find out the date and time right now or to store past or future dates

  • NSData

    • A “bag of bits”

Data Structures

Three Types: Classes, Structures, Enumerations

  • Similarities

    • Declasration syntax
    • Properties and Functions
    • Initializers

  • Differences

    • Inheritance (class only)
    • Introspection and casting (class only)
    • Value type (struct, enum) vs. Reference type (class)

Value vs. Reference

  • Value (struct and enum)

    • Copied when passed as an argument to a function
    • Copied when assigned to a different variable
    • Immutable if assigned to a variable with let
    • Remember that function parameters are, by default, constants
    • You can put the keyword var on an parameter, and it will be mutable, but it’s still a copy
    • You must note any func that can mutate a struct/enum with the keyword mutating

  • Reference (class)

    • Stored in the heap and reference counted (automatically)
    • Constant pointers to a class (let) still can mutate by calling methods and changing properites
    • When passed as an argument, does not make a copy (just passing a pointer to same instance)

  • Choosing which to use?

    • Usually you will choose class over struct. struct tends to be more for fundamental types. Use of enum is situational (any time you have a type of data with discret values)

AnyObject

  • Special “Type” (actually it’s a Protocol)

    • Used primarily for compatibility with exsiting Objective-C-based APIs

  • Where will you see it?

    • As properties (eigher singularly or as an array of them), e.g. …
    • var destinationViewController: AnyObject
    • var toolbarItems: [AnyObject]

  • How do we use AnyObject

    • We don’t usually use it directly
    • Instead, we convert it to another, known type

  • How do we convert it?

    • We need to create a new vairable which is of a known object type

  • Casting AnyObject

    • We “force” an AnyObject to be something else by “casting” it using the as keyword

总结

语言的细节还有很多，需要在实践中不断熟悉，这里不需要过度在意细节，动手最重要

5 Objective C Compatibility, Property List, Views

  • 主要介绍了 Swift 与 Objc 的桥接，这里官方的指南都有介绍，具体不赘述

  • Property List is really just the definition of a term

    • pass around data “blindly”
    • “generic data structure”, be passed to API
    • example: NSUserDefaults, small database
    • 持久化的方式

  • Views

    • UIView subclass

    • Defines a coordinate space, for drawing, and for handling touch events

    • Hierarchical (only one superview, but many/zero subviews)

    • The hierarchy is most often constructed in Xcode graphically

      • But it can be done in code as well

    • Where does the view hierarchy start?

      • THe top of the (usable) view hierarchy is the Controller’s var view: UIView
      • This view is the one whose bounds will change on rotation
      • This view is likely the ones you will programmatically add subview to
      • All of your MVC’s View’s UIView will have this view as an ancestro
      • It’s wutomatically hooked up for you when you create an MVC in Xcode

    • 在代码中初始化 UIView 需要实现两个必要 init 函数，因为有两种方式可以创建

    • 或者也可以用 awakeFromNib 针对 storyboard

  • View Coordinate System

    • Origin is upper left

    • Units are points, not pixels

      • Pixels are the minimum-sized unit of drawing your device is capable of
      • Points are the units in the coordinate system
      • Most of the time there are 2 pixels per point, but it could be only 1 or something else
      • How many pixels per point are there? UIView‘s var contentScaleFactor: CGFloat

    • The boundaries of where drawing happends

      • var bounds: CGRect // a view’s internal drawing space’s origin and size
      • This is the rectangle containing the drawing space in its own coordinate system
      • It is up to your views’ implementation to interpret what bounds.origin means (often nothing)

    • Where is the UIView? 注意都是在 superview 里的，不是自己的

      • var center: CGPoint // the center of a UIView in its superview’s coordinate system
      • var frame: CGRect // the rect containing a UIView in its superview’s coordinate system

  • bounds vs frame

    • Use frame and/or center to position a UIView
    • frame.size 不总是等于 bounds.size -> 因为旋转的时候 frame 要大得多！

  • Creating Views

    • Most often your views are created via your storyboard
    • To draw, just create a UIView subclass and override drawRect
    • NEVER call drawRect!! EVER! Or else!

  • 绘制的方法也有很多，主要是 Bezier 已经一些 UIKit 的设定

  • UIColor: RGB, HSB or even a pattern (using UIImage)

    • have alpha (transparency) 0(fully transparent) 1.0(fully opaque)
    • 如果需要透明需要把 UIView 的 var opaque = false

  • Drawing Text

    • Usually we use a UILabel to put text on screen
    • To draw in drawRect, use NSAtrributedString
    • Mutability is done with NSMutableAttributedString
    • NSattributedString is not a String, nor an NSString

  • Fonts

    • The absolutely best way to get a font in code

      • `class func preferredFontForTextStyle(UIFontTextStyle) -> UIFont
      • UIFontTextStyle.Headline
      • UIFontTextStyle.Body
      • UIFontTextStyle.Footnote

    • There are also “system fonts”

      • Don’t use for user’s content. Use preferred fonts for that

  • 在 storyboard 中按着 ctrl + shift 再点击控件会出现一个界面让你选择你想要选择的控件，很有用

  • 如果需要在更新某个值的时候同时更新绘制，利用 didSet 方式声明变量

  • 如果需要一个 view 在旋转之后更新，在其 attribute inspector 中把 Mode 改为 Redraw

6 Protocols and Delegation, Gestures

  • 在一个 UIView 的代码前加上 @IBDesignable 可以直接在 storyboard 中绘制图案

  • 在一个 UIView 中的变量前加上 @IBInspectable 就可以直接在 storyboard 中更改

  • Extension 只能添加，不能修改原来的方法或者属性

    • 是一个很容易滥用的机制！注意场景

  • Protocol - A way to express an API minimally

    • is a TYPE just like any other type, except

      • It has no storage or implementation associated with it
      • 没有对应的实现，只是一个羊头，没有狗肉

  • Delegation

    • A very important use of protocols

    • How it plays out

      • Create a delegation protocol (defines what the View wants the Controller to take care of)
      • Create delegate property in the View whose type is that delegation protocol
      • Use the delegate property in the View to get/do things it can’t own or control
      • Controller declares that it implements the protocol
      • Controller sets self as the delegate of the View by setting the property in #2 above
      • Implement the protocol in the Controller

    • Now the View is hooked up to the Controlle

    • weak 用来避免循环引用

    • let smiliness = dataSource?.smilinessForFaceView(self) ?? -0.0

      • ?? 符号表示，如果左边的表达式是 nil，那么用右边的值

    • comman + shift + o 可以快速检索并打开文件

  • Gestures

    • we can get notified of the raw touch events

    • Gestrues are recognized by instances of UIGestureRecognizer

    • Two sides to using a gesture recognizer

      1. Adding a gesture recognizer to a UIView
      2. Providing a method to “handle” that gesture

    • Usually the first is done by a Controller

    • The second is provided either by the UIView or a controller

  • UISplitViewController (Two MVCs side by side)

    • 左边 Master，右边 Detail

7 Multiple MVCs

  • UINaviationController

    • Pushes and pops MVCs off of a stack
    • 只有顶上的 title bar 是 UINavigationController 绘制的
    • rootViewController 用来切换显示不同的 MVC

  • You can get the sub-MVCs via the viewControllers property

    • `var viewControllers: [UIViewController] { get set }

  • Every UIViewController knows the Split View, Tab Bar or Navigation Controller it is currently in

  • Wirting up MVCs

    • ctrl + drag in storyboard
    • 当然也可以在代码中实现，不过这个课程里只用 storyboard，我个人也觉得交给 storyboard 就好
    • Editor -> Embed in -> Navigation Controller

  • Segue

    • Four Basic Segues
    • Show Segue, Show Detail Segue, Modal Segue(better not), Popover Segue
    • always create a new instance of an MVC，不会用已有的
    • 要保证 identifier 和代码里用的一致
    • More important use of the identifier: preparing for a segue

  • Preparing for a Segue

    • It is crucial to understand that this preparation is happening BEFORE outlets get set!
    • It is a very common bug to prepare an MVC thinking its outlets are set

  • Preventing Segues

    • You can prevent a segue from happening too
    • shouldPerformSegueWithIdentifier 返回 false 即可

  • Label 的 Autoshrink 属性可以避免出现文字过长

  • Popovers

    • Popovers pop an entire MVC over the rest of the screen
    • is not a UIViewController
    • Things to note when preparing for a popover segue
    • popOverPresentationController 针对 iphone 和 ipad 有不同的表现形式，但是也是可以自由定制的，有对应的方法

  • override 基类的 property 的 didSet 方法不会覆盖原来的，而是在原来的基础上添加

8 View Controller Lifecycle, Autolayout

  • After instantiation and outlet-setting, viewDidLoad is called

    • This is an exceptionally good place to put a lot of setup code
    • It’s better than an init because your outlets are all set up by the thime this is called
    • update your UI from your model
    • but geometry of your view (bounds) is not set yet!

  • Just before your view appears on screen, you get notified

    • func viewWillAppear(animated: Bool)
    • don’t pu something in this method that really wants to be in viewDidLoad
    • Do something here if things your display is changing while your MVC is off-screen
    • Your view’s geometry is set here, but there are other plaes to react to geometry

  • You get notified when you will disappear off screen too

    • This is where you put “remember what’s going on” and cleanup code

  • Geometry changed?

    • Most of the time this will be automatically handled with Autolayout

    • But you can get involved in geometry changes directly with

      • func viewWillLayoutSubviews()
      • Autolayout happens between these two method
      • func viewDidLayoutSubviews()

  • Autorotation

    • You can control which orientations your app supports in the Settings of your project
    • Almost always, your UI just responds naturally to rotation with autolayout

  • In low-memory situations, didReceiveMemoryWarning get called

  • awakeFromNib

    • This method is sent to all objects that come out of a storyboard (including your Controller)
    • Happens before outlets are set!
    • Put code somewhere else if at all possible

  • Size Classes

    • Compact, Regular, Any
    • 可以在 storyboard 中进行不同组合的配置，下面也会有说明
    • 可以在 Inspector 里设置不同控件和 constrain 的范围（最下面的部分）

9 ScrollView and Multithreading

  • 先设置 scrollView 的 contentSize，然后就可以正常添加不同的 frame

  • 注意不同坐标系的转换

  • UIScrollView

    • add your “too big” UIView in code using addSubview
    • Now don’t forget to set the contentSize

  • Scolling programmatically

    • func scrollRectToVisible(CGRect, animated: Bool)

  • Zooming (affine transform)，可以设置最大最小的放大

    • Will not work without delegate method to specify view to zoom
    • 也可以编程 zoom

  • Closure

    • capture variables in the surrounding context
    • can lead to very elegant code
    • 使用时需要小心，因为可能会出现循环引用 [unowned self] in ...

  • Queues

    • Multithreading is mostly about “queues” in iOS.
    • Functions (usually closures) are lined up in a queue.
    • Then thos functions are pulled off the queue and executed on an associated thread

  • Main Queue

    • All UI activity MUST occur on this queue and this queue only.
    • non-UI activity that is at all time consuming must NOT occur on that queue.
    • We want our UI to be responsive!
    • Functions are pulled off and worked on in the main queue only when it is “quiet”
    • dispatch)async(queue) 执行完成后再 dispatch main queue 以更新 UI

  • Other Queue 不同的优先级

    • QOS_CLASS_USER_INTERACTIVE // quick and high priority
    • QOS_CLASS_USER_INITIATED // high priority, might take time
    • QOS_CLASS_UTILITY // long running
    • QOS_CLASS_BACKGROUND // user not concerned with this

  • 还可以执行一些延迟排队的任务

10 Table View

  • UITextField

    • Like UILabel, but editable
    • Keyboard appear when UITextField becomes “first responder”
    • becomeFirstResponder and resignFirstResponder
    • Delegate can get involved with Return key, etc

  • UITableView

    • displayer data in a table

    • one-dimensional table

    • subclass of UIScrollView

    • Displaying multi-dimensional tables

      • uaually done via a UINavigationController with multiple MVC’s where View is UITableView

    • Group style and plain style

    • Table Header, Table Footer, Section, Section header

    • Subtitle, Basic, Right Detail, Left Detail

  • UITableViewCell 用来自定义

  • 两个重要部分 delegate 和 dataSource，如果需要动态的列表

  • dequeueReusableCellWithIndentifier 来重用 cell

  • UITableViewDataSource

    • Number of sections is 1 by default
    • No default for numberOfRowsInSection
    • do not implement these dataSource method for a static table

  • Loading your table view with data

    1. set the table view’s dataSource to your Controller (automatic with UITableViewController)
    2. implement numberOfSectionsInTableView and numberOfRowsInSection
    3. implement cellForRowAtIndexPath to return loaded-up UITableViewCells

  • UITableView Target/Action

    • UITableViewDelegate method sent when row is selected
    • func reloadData()

  • 这一部分很重要，要重点掌握

11 Unwind Segues, Alerts, Timers, View Animation

  • Unwind Segue

    • The only segue that does NOT create a new MVC
    • Jumping up the stack of cards in a navigation controller
    • Dismissing a Modally segued-to MVC while reporting information back to the presenter
    • ctrl+drag to the exit icon

  • Alerts and Action Sheets

    • pop up and ask the user something mechanism

  • Alerts

    • Pop up in the middle of the screen
    • Usually ask questions with only two(or one) answers
    • Can be disruptive to your user-iterface, so use carefully
    • Often used for “asynchronous” problems
    • Can have a text field to get a quikc answer

  • Action Sheets

    • Usually slide in from the bottom of the screen on iPhone, and in a popover on iPad
    • Can be displayed from bar button item or from any rectangular area in a view
    • Generally asks questions that have more than two answers

  • Timer NSTimer

    • Setting up a timer to call a method periodically
    • more for larger-grained activities
    • It might help system performance to set a tolerance for “late firing”
    • the firing time is relative to the start of the timer

  • Kinds of Animation

    • Animating UIView properties
    • Animation of View Controller transition
    • Core Animation

  • UIView Animation

    • Change to certain UIView properties can be animated over time

      • frame, transform(translation, rotation and scale), alpha(opacity)

    • Done with UIView class method(s) using closure

    • animateWithDuration

    • UIViewAnimationOptions: BeginFromCurrentState, AllowUserInteraction, LayoutSubview, Repeat, Autoreverse, OverrideInheritedDuration, OverrideInheritedCurve, AllowAnimatedContent, CurveEaseInEaseOut, CurveEaseIn, CurveLinear

    • Sometimes you want to make an entire view modification at once

    • Use closures again with this UIView class method

12 Dynamic Animation

  • Set up physics relating animatable objects and let them run until they resulve to stasis

  • Steps

    • Create a UIDynamicAnimator
    • Add UIDynamicBehaviros to it (gravity, collisions, etc)
    • Add UIDynamicItems (usualy UIViews) to the UIDynamicBehaviors

  • UIGravityBehavior

    • angle, magnitude

  • Stasis

    • UIDynamicAnimator‘s delegate tells you when animation pauses
    • dynamicAnimatorDidPause(UIDynamicAnimator)

13 Application Lifecycle and Core Motion

  • Notification

    • For Model (or global) to Controller communication
    • NSnotificationCenter，类似一个观察者模式，注册并获取变动时的通知

  • Application Lifecycle

    • Not running, Inactive, Active, Background, Suspended
    • application(UIApplication, didFinishLauchingWithOptions: [NSObject: AnyObject])
    • 用来知道自己的 app 是在什么情况下被打开的（不只是用户点击这一种）

  • UIApplication

    • Shared instance

      • manages all global behavior
      • never need to subclass it
      • It delegates everything you need to be involved in to its UIApplicationDelegate

  • Info.plist

    • Many of your application’s settings are in Info.plist

  • Capabilities

    • Some features require enabling (iCloud, Game Center, etc)
    • Switch on in Capabilities tab (Inside your Project Settings)

  • Airdrop 需要先注册，参考 Trak 的 info.plist

  • Core Motion

    • API to access motion sensing hardware on your device

    • Primary inputs: Accelerometer, Gyro, Magnetometer

    • Class used to get this input is CMMotionManager

    • Usage

      • Check to see what hardware is available
      • Start the sampling going and poll the motion manager for the latest sample it have
      • …or…
      • check to see what hardware is available
      • Set the rate at which you want data to be reported from the hardware
      • Register a closure (and a queue to run it on) to call each time a sample is taken

    • Checking availability of hardware sensor

      • var {accelerometer, gyro, magnetometer, deviceMotion}Available: Bool

    • Starting the hardware sensors collecting data

      • you only need to do this if you are going to poll for data
      • func start{Accelerometer, Gyro, Magnetometer, DeviceMotion}Updates()

    • Is the hardware currently collection data?

      • var {accelerometer,gyro,magnetometer,deviceMotion}Active: Bool

    • Stop the hardware collecting data

      • func stop{Accelerometer,Gyro,Magnetometer,DeviceMotion}Updates()

  • CMDeviceMotion

    • 各种传感器的组合

14 Core Location and MapKit

  • Core Location

    • Framework for managing location and heading

      • No user-interface

    • Basic object is CLLocation

      • Properties: coordinate, altitude, horizontal/verticallAccuracy, timestamp, speed, course

  • The more accuracy you request, the more battery will be used

  • CLLocationManager

    • Check if the hardware you are on/user supports the kind of location updating you want
    • Create a CLLocationManager instance and set the delegate to receive updates
    • Configure the manager according to what kind of location updating you want
    • Start the manager monitoring for location changes

  • Kinds of location monitoring

    • Accuracy-based continual updates
    • Updates only when “significant” changes in location occur
    • Region-based updates
    • Heading monitoring

  • Asking CLLocationManager what your hardware can do

    • class func authorizationStatus() -> CLAuthorizationStatus // Authorized, Denied or Restricted
    • class func locationServicesEnabled() -> Bool // user enabled (or not) locations for your app

  • You must add an Info.plist entry

    • NSLocationWhenInUseUsageDescription
    • NSLocationAlwaysUsageDescription

  • Error reporting to the delegate

    • func locationManager(CLLocationManager, didFailWithError: NSError)
    • Not always a fatal thing, so pay attention to this delegate method

  • 也可以进行后台更新

  • Map Kit

    • UI, can have annotations on it
    • Each annotation is a coordinate, a title and a subtitle
    • Annotation can have a callout. It appears when the annotation view is clicked
    • import MapKit
    • 地图部分也是玩法很多的，需要仔细研究研究

  • MKLocalSearch

    • Can search by natural language strings asynchronously

  • MKDirections, MKRoute, MKPolyline

  • Overlays, MKOverlayView

  • callout 只能代码配合 storyboard 实现，因为 storyboard 压根不会显示这个 callout

15 Modal Segues

  • Modal View Controller

    • A way of segueing that takes over the screen (should be used with care)
    • Example (Contacts application)
    • No back button (only Cancel)

  • Hearing back from a Modally segue-to View Controller

    • To communicate results, generally you would Unwind (though delegation possible too)
    • func dismissViewControllerAnimated(Bool, completion: () -> Void)
    • Remember that unwind automatically dismisses

  • How is the modal view controller animated

    • var modalTransitionStyle: UIModalTransitionStyle
    • .CoverVertical, .FlipHorizontal, .CrossDissolve, .PartialCurl

16 Camera, Persistence and Embed Segues

  • UIImagePickerController

    • Modal view to get media from camera or photo library

    • Usage

      1. Create it & set its delegate
      2. Configure it (source, kind of media, user edibility)
      3. Present it
      4. Respond to delegate method when user is done/cancels picking the media

    • Sources: .PhotoLibrary, .Camera, .SavedPhotosAlbum

    • kUTTypeImage, kUTTypeMovie from import MobileCoreServices

  • 相机这部分等移植图像处理库的时候再细细研究

  • Persistence

    • Archiving, SQLite, File System, Core Data

  • Archiving

    • A mechanism for making ANY object graph persistent
    • Requires all object in the graph to implement USCoding protocol

  • SQLite

    • SQL in a single file
    • Fast, low memory, reliable
    • Open SOurce, comes bundled in iOS
    • Not good for everything
    • Not a server-based technology
    • In used by Core Data

  • File System

    • Acess files in the Unix filesystem

      1. Get the root of a path into an NSURL
      2. Append path componnets to the URL
      3. Write to/read from the files
      4. Manage the filesystem with NSFileManager

    • You can only write inside your application’s sandbox

      • Security, Privacy, Cleanup

  • Core Data

    • Object-oriented database

    • Very, very powerful framework in iOS

    • How does it work?

      • Create a visual mapping (using Xcode tool) between database and objects
      • Create and query for objects using object-oriented API
      • Access the “columns in the database table” using @NSManaged vars on those objects

  • Embed Segues

    • Putting a VC’s self.view in another VC’s view hierarchy
    • This can be a very powerful encapsulation technique
    • Drag out a `Container View from the object palette into the scene you want to embed it in
    • Automatically sets up an “Embed Segue” from container VC to the contained VC
    • The embedded VC’s outlets are not set at the time prepareForSegue(sender:) is called

17 Internationalization and Settings

  • Two steps to making international versions of your application

    • Internationalization (i18n)
    • Localization (l10n)

  • Internationalization

    • This is a process of making string externally editable (from storyboard or code)
    • It also involves using certain “formatting” classes for things like dates, number, etc

  • Localization

    • A process of translating those externalized strings for a given language

  • Storyboards are localized by changing the strings inside only

    • And we rely on Autolayout to make it all look nice

  • First step: Registering Localizable Languages

    • Go to the Project pane in Xcode then Info tab to add Localizations
    • 注意是 project 不是 target

  • Formatters

    • locale, region of the world
    • It is separate from language
    • In different regions some things might display differently: numbers, dates, currency, etc
    • 有各种 Formatter，可以仔细看看
    • Date 是一个比较难处理的，需要注意

  • UIImage

    • There are a number of ways to approach this.
    • The image files themselves (if not in Images.xcassets) can be made localizable (File Inspector)
    • Or you can keep them in Images.scassets and use NSLocalizedString for the image name

  • Editor -> Export For Localization

    • .xliff cantain all of your resources

  • 可以创建不同的 scheme 来以不同的语言来运行 app

  • Settings

    • A little bit of UI for your application
    • 在类似 Info.plist 里进行创建 -> Settings Bundle
    • 创建时会有一个例子，是很好的参考学习方式
    • 每个 item 有 identifier

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