195 lines
3.3 KiB
Swift
195 lines
3.3 KiB
Swift
import UIKit
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var greeting = "Hello, playground"
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//: [Previous](@previous)
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//: ## 区间运算符
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//: ### 闭区间运算符
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/*:
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闭区间运算符：
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a...b : a <= 取值 <= b
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*/
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let names = ["Anna", "Alex", "Brian", "Jack"]
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for i in 0...3 {
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print(names[i])
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}
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let a = 1
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var b = 3
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for i in a...b {
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print(names[i])
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}
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let range = 1...3
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for i in range {
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print(names[i])
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}
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// i默认是let，有时需要声明为var
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for var i in 1...3 {
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// i的值可以发生变化
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i += 5
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print(i)
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}
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// 用不上变量,可以用_进行忽略
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for _ in 1...3 {
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print("123456")
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}
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//: ### 半开区间运算符
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/*:
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半开区间运算符
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a..<b : a <= 取值 < b
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*/
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//: ### 单侧区间运算符
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/*:
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单侧区间运算符
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a... : a <= 取值
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...b : 取值 <= b
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*/
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//: ### 区间类型
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// 闭区间 ClosedRange
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let range1: ClosedRange<Int> = 1...3
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// 半开区间 Range
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let range2: Range<Int> = 1..<3
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// 单侧区间 PartialRangeThrough
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let range3: PartialRangeThrough<Int> = ...5
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//: ### 带间隔的区间值
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// 使用函数stride
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for tickMark in stride(from: 4, to: 11, by: 2) {
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print(tickMark)
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}
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//: ## switch
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/*:
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switch注意点
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- switch必须保证能处理所有的情况
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- 能处理所有情况的下，可以省略default
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- switch 也支持Character、String类型
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- switch 支持区间匹配以及元组匹配
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*/
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// 默认可以不写break，并不会贯穿到后面的条件
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var num = 1
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switch num {
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case 1:
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print("number is 1")
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case 2:
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print("number is 2")
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default:
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print("number is other")
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}
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// 使用fallthrough可以实现贯穿效果
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var number = 1
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switch number {
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case 1:
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print("number is 1")
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fallthrough
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case 2:
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print("number is 2")
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default:
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print("number is other")
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}
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//: #### 区间匹配
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let count = 62
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switch count {
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case 0:
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print("none")
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case 1..<5:
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print ("a few")
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case 5..<12:
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print("several")
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case 12..<100:
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print("dozens of")
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case 100..<1000:
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print("hundreds of")
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default:
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print("many")
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} // dozens of
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//: #### 元组匹配
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// 可以使用下划线_ 忽略某个值
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let point = (1, 1)
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switch point {
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case (0, 0):
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print("the origin")
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case (_, 0):
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print ("on the x-axis")
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case (0, _):
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print("on the y-axis")
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case (-2...2, -2...2):
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print("inside the box")
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default:
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print( "outside of the box")
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}
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//: ### 值绑定
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// 必要时 let 可以换为 var
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let point1 = (2, 0)
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switch point1 {
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case (let x, 0):
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print("on the x-axis with a x value of \(x)")
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case (0, let y):
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print("on the y-axis with a y value of \(y)")
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case let(x, y):
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print("somewhere else at (\(x), \(y))")
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}
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//: ### where
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// 1. 用在case的后边
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let point2 = (1, -1)
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switch point2 {
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case let(x, y) where x == y:
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print("on the line x == y")
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case let(x, y) where x == -y:
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print("on the line x == -y")
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case let(x, y):
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print("somewhere else at (\(x), \(y))")
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}
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//2. 对数据进行过虑
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var numbers = [10, 20, 30, -10, -30]
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var sum = 0
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for num in numbers where num > 0 {
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sum += num;
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}
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print(sum)
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//: ### 标签语句
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// 标签语句是
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// 标签: 代码
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outer: for i in 1...4 {
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for k in 1...4 {
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if k == 3 {
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continue outer
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}
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if i == 3 {
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break outer
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}
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print("i == \(i), k == \(k)")
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}
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}
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//: [Next](@next)
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