Swift 笔记 ｜ Language Guide

阅读The Swift Programming Language (5.7) - Language Guide的笔记

The Basics

• fundamental types Int Double Float Bool String
• collection types Array Set Dictionary

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Swift is a type-safe language, which means the language helps you to be clear about the types of values your code can work with.

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declare multiple constants or multiple variables on a single line:

var x = 0.0, y = 0.0, z = 0.0

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let minValue = UInt8.min
let maxValue = UInt8.max

Int在32bit和64bit的操作系统上分别为Int32和Int64

推荐日常使用Int、Double

二进制：0b 八进制：0o 十六进制：0x

1.25e2 0xFp-2 p表示十六进制的指数

_可以作为数字的分隔符

typealias AudioSample = UInt16

let a = (code: 200, description: "OK")

assert() precondition() 早期开发可以用fatalErros("Unimplemented")

Basic Operators

主动溢出a &+ b

-9 % 4 = 1

可以使用+=

元组的比较按照元组的先后顺序来挨个比较

可以使用? :表达式

a != nil ? a! : b -> a ?? b

... ..< [2...] [...2]

Strings and Characters

Collection Types

Control Flow

Functions

Closures

Enumerations

enum Planet {
    case mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
}

print(Planet.allCases)

enum Barcode {
    case upc(Int, Int, Int, Int)
    case qrCode(String)
}

recursive enumerations: indirect enum 示例：算术表达式计算

indirect enum ArithmeticExpression {
    case number(Int)
    case addition(ArithmeticExpression, ArithmeticExpression)
    case multiplication(ArithmeticExpression, ArithmeticExpression)
}

Structures and Classes

其中的东西叫properties和methods

由于structure和class在Swift里面差不多，实例化得到的对象object被称作instance

class有而structure没有：继承、casting类型转换、析构、引用instance

“As a general guideline, prefer structures because they’re easier to reason about, and use classes when they’re appropriate or necessary. In practice, this means most of the custom data types you define will be structures and enumerations. For a more detailed comparison, see Choosing Between Structures and Classes.” Consider the following recommendations to help choose which option makes sense when adding a new data type to your app. * Use structures by default. * Use classes when you need Objective-C interoperability. * Use classes when you need to control the identity of the data you're modeling. * Use structures along with protocols to adopt behavior by sharing implementations. 由于类的实例可以引用，所以如果要在App中的多个地方修改一个东西，那么这个东西就可以用类来描述

“All structures and enumerations are value types in Swift. This means that any structure and enumeration instances you create—and any value types they have as properties—are always copied when they’re passed around in your code.” 注意数组字符串字典这些都是拷贝 class为reference type

Swift一般不用指针，除非你想手动管理内存

Properties

Methods

Subscripts

Inheritance - Class

Initialization

Deinitialization - Class

Optional Chaining

Error Handling

Concurrency

Type Casting - Class

Nested Types

Extensions

Protocols

Generics

Opaque Types

Automatic Reference Counting - Class

Memory Safety

Access Control

Advanced Operators