Swift4.0新特性（上）

2017-06-14 本文已影响2632人 Mg明明就是你

The Swift Programming Language (Swift 4)

Swift的180个介绍

Range

//: # 一、更便捷的Range
var str = "Hello, playground"
// Swift3.0
var index = str.index(of: " ")!
let greeting = str[str.startIndex ..< index]
index = str.index(index, offsetBy: 1) // index 下标 +1
let name = str[index ..< str.endIndex]
// Swift4.0
var index1 = str.index(of: " ")!
let greeting1 = str.prefix(upTo: index1)
index1 = str.index(index1, offsetBy: 1)
let name1 = str.suffix(from: index1)
print(Array(str.enumerated()))
print(Array(zip(1..., str)))

截图展示.png

二、Str的变化一个集合类型

简介

var str = "Hello, playground"
print(str.characters.count) // Swift3.0写法
print(str.count)            // Swift4.0写法
/// 遍历
str.forEach {
        $0
}

多行文字 (""" """)

/// plist格式
let plistInfo = """
<?xml version="1.0" encoding="UTF-8"?>
<plist version="1.0">
<array>
      <dict>
          <key>title</key>
              <string>设置WiFi</string>
          <key>imageName</key>
              <string>serversSet</string>
      </dict>
</array>
</plist>
"""
/// JSON格式
let jsonInfo = """
{
      "data": {
          "title": "String is a collection"
          "author": "23"
          "creat_at": "2017-06-13"
      }
}
"""
print(plistInfo)
print(jsonInfo)

打印结果.png

三、改进的private的访问权限

//: # 改进的private的访问权限（扩展中可以访问private修饰的变量了）
class Person {
    fileprivate var name: String = "MG"
    private var age = 23
}
extension Person {
    func change() {
        name = "明明"
        age = 32
    }
}
let person = Person()
person.change()

截图展示.png

四、更智能安全的Key Value Coding

//: # 更智能安全的Key Value Coding
class Weather: NSObject {
    @objc var months = 12
    @objc var season = "Spring"
    @objc var seasones = ["Spring","Summer","Autumn;","winter"]
}
/// Swift4之前的写法
let w = Weather()
w.season = "Summer"
var season = w.value(forKeyPath:  "season")
w.setValue("Autumn", forKeyPath: "season")
/// Swift4.0
let seasonKeyPath = \Weather.season
var season1 = w[keyPath: seasonKeyPath]
w[keyPath: seasonKeyPath] = "MG明明"