Swift 4 Cheat Sheet and Quick Reference

最新推荐文章于 2019-08-21 23:37:25 发布

henrychen8888

最新推荐文章于 2019-08-21 23:37:25 发布

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本文链接：https://blog.youkuaiyun.com/u013027945/article/details/81217962

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本文介绍了Swift编程语言的基础知识，包括类实现、方法定义、实例创建与使用、枚举类型、变量声明与类型介绍、控制流结构、字符串操作、数组与字典的使用等核心概念。

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## Class Implementation

```swift
class MyClass : OptionalSuperClass, OptionalProtocol1, OptionalProtocol2 {
var myProperty:String
var myOptionalProperty:String?
// More properties...

// Only need override if subclassing
override init() {
myProperty = "Foo"
}
// More methods...
}
```

## Methods

```swift
func doIt() -> Int {
   return 0
}
func doIt(a:Int) -> Int {
   return a
}
func doIt(a:Int, b:Int) -> Int {
   return a+b
}
```

## Creating/Using an Instance

```swift
var a = MyClass()
a.myProperty
a.doIt()
a.doIt(a:1)
a.doIt(a:2, b:3)
```

## Enums

```swift
enum CollisionType: Int {
case player = 1
case enemy = 2
}
var type = CollisionType.player
```

## Declaring Variables

```swift
var mutableDouble:Double = 1.0
mutableDouble = 2.0

let constantDouble:Double = 1.0
// constantDouble = 2.0 // error

var mutableInferredDouble = 1.0

var optionalDouble:Double? = nil
optionalDouble = 1.0
if let definiteDouble = optionalDouble {
definiteDouble
}
```

## Variable types

## Control Flow

```swift
var condition = true
if condition {
} else {
}

var val =5
switch val {
case 1:
   "foo"
case 2:
   "bar"
default:
   "baz"
}

// omits upper value, use ... to include
for i in 0..<3 { }
```

## String Quick Examples

```swift
var personOne = "Ray"
var personTwo = "Brian"
var combinedString = "\(personOne): Hello, \(personTwo)!"

var tipString = "2499"
var tipInt = Int(tipString)

tipString = "24.99"
var tipDouble = Double(tipString)
```

## Array Quick Examples

```swift
var person1 = "Ray"
var person2 = "Brian"
var array:[String] = [person1, person2]
array.append("Waldo")

for person in array {
print("Person: \(person)")
}
var waldo = array[2]
```

## Dictionary Quick Examples

```swift
var dict:[String: String] = ["Frog": "Kermit", "Pig": "Ms. Piggy", "Weirdo": "Gonzo" ]
dict["Weirdo"] = "Felipe"
dict["Frog"] = nil // delete frog

for (type, muppet) in dict {
print("type: \(type), muppet: \(muppet)")
}
```

## Reference

[https://koenig-media.raywenderlich.com/uploads/2014/06/RW-Swift-Cheatsheet-0_8.pdf](https://koenig-media.raywenderlich.com/uploads/2014/06/RW-Swift-Cheatsheet-0_8.pdf)