運(yùn)算符是用來檢查，更改或組合值的特殊符號(hào)或短語(yǔ)。Swift提供的很多常規(guī)的運(yùn)算符，如+、-、*、/、%、=、==等，以及邏輯運(yùn)算的&&、||等等，基本上不需要重復(fù)介紹，我們?cè)谶@里只需要了解一些不太一樣的運(yùn)算符就可以了。如Swift引入的新運(yùn)算符，范圍操作符號(hào)，包括..<和...兩個(gè)，該隨筆介紹Swift常規(guī)的運(yùn)算符中，以及和其他語(yǔ)言有所差異的部分。

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賦值運(yùn)算符

let b = 10 var a = 5 a = b // a is now equal to 10

?賦值語(yǔ)句，處理和其他語(yǔ)言一樣。

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let (x, y) = (1, 2) // x is equal to 1, and y is equal to 2

?這種代碼是類似ECMAScript 6的腳本寫法，通過把右邊元祖對(duì)象解構(gòu)賦值給左邊對(duì)應(yīng)的參數(shù)。

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數(shù)學(xué)運(yùn)算符

1 + 2 // equals 3 5 - 3 // equals 2 2 * 3 // equals 6 10.0 / 2.5 // equals 4.0

?這些都是和其他語(yǔ)言沒有什么不同，循例列出參考下

對(duì)于字符，也可以使用+符號(hào)進(jìn)行連接新的字符串

"hello, " + "world" // equals "hello, world"

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一元操作符中的-、+運(yùn)算，和算術(shù)里面的負(fù)負(fù)得正，正負(fù)得負(fù)的意思一樣了。

let three = 3 let minusThree = -three // minusThree equals -3 let plusThree = -minusThree // plusThree equals 3, or "minus minus three"

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let minusSix = -6 let alsoMinusSix = +minusSix // alsoMinusSix equals -6

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組合運(yùn)算符提供+= 、-=的運(yùn)算符操作

var a = 1 a += 2 // a is now equal to 3

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對(duì)比運(yùn)算符和其他語(yǔ)言差不多

• 等于 (a == b)

• 不等于 (a != b)

• 大于 (a > b)

• 小于 (a < b)

• 大于等于 (a >= b)

• 小于等于 (a <= b)

另外值得注意的是，Swift提供了對(duì)比引用的兩個(gè)操作符號(hào)，===?和?!==，用來檢查兩個(gè)引用是否完全相等；或者不相等的。而==只是用來對(duì)比兩個(gè)對(duì)象的值是否一致。

1 == 1 // true because 1 is equal to 1 2 != 1 // true because 2 is not equal to 1 2 > 1 // true because 2 is greater than 1 1 < 2 // true because 1 is less than 2 1 >= 1 // true because 1 is greater than or equal to 1 2 <= 1 // false because 2 is not less than or equal to 1

?對(duì)比運(yùn)算符也經(jīng)常用來If條件語(yǔ)句里面

let name = "world" if name == "world" {print("hello, world") } else {print("I'm sorry \(name), but I don't recognize you") } // Prints "hello, world", because name is indeed equal to "world".

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三元運(yùn)算符

三元運(yùn)算符 ？ ：和C#里面表現(xiàn)是一樣的

question ? answer1 : answer2

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let contentHeight = 40 let hasHeader = true let rowHeight = contentHeight + (hasHeader ? 50 : 20)

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空值轉(zhuǎn)換操作符

空值轉(zhuǎn)換符是對(duì)可空類型（可選類型）的一個(gè)值得轉(zhuǎn)換出來(a ?? b)。

let defaultColorName = "red" var userDefinedColorName: String? // defaults to nilvar colorNameToUse = userDefinedColorName ?? defaultColorName // userDefinedColorName is nil, so colorNameToUse is set to the default of "red"

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userDefinedColorName = "green" colorNameToUse = userDefinedColorName ?? defaultColorName // userDefinedColorName is not nil, so colorNameToUse is set to "green"

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范圍操作符

閉合范圍運(yùn)算符 ... 和半閉合范圍運(yùn)算符 ..< 兩個(gè)

for index in 1...5 {print("\(index) times 5 is \(index * 5)") } // 1 times 5 is 5 // 2 times 5 is 10 // 3 times 5 is 15 // 4 times 5 is 20 // 5 times 5 is 25

?半閉合的范圍運(yùn)算符

let names = ["Anna", "Alex", "Brian", "Jack"] let count = names.count for i in 0..<count {print("Person \(i + 1) is called \(names[i])") } // Person 1 is called Anna // Person 2 is called Alex // Person 3 is called Brian // Person 4 is called Jack

?或者如下使用

for name in names[..<2] {print(name) } // Anna // Alex

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以及一側(cè)范圍的運(yùn)算符，包括左側(cè)和右側(cè)兩個(gè)部分

for name in names[2...] {print(name) } // Brian // Jackfor name in names[...2] {print(name) } // Anna // Alex // Brian

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let range = ...5 range.contains(7) // false range.contains(4) // true range.contains(-1) // true

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邏輯運(yùn)算符

let allowedEntry = false if !allowedEntry {print("ACCESS DENIED") } // Prints "ACCESS DENIED"

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let enteredDoorCode = true let passedRetinaScan = false if enteredDoorCode && passedRetinaScan {print("Welcome!") } else {print("ACCESS DENIED") } // Prints "ACCESS DENIED"

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let hasDoorKey = false let knowsOverridePassword = true if hasDoorKey || knowsOverridePassword {print("Welcome!") } else {print("ACCESS DENIED") } // Prints "Welcome!"

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if enteredDoorCode && passedRetinaScan || hasDoorKey || knowsOverridePassword {print("Welcome!") } else {print("ACCESS DENIED") } // Prints "Welcome!"

或者使用括號(hào)使之更加方便閱讀

if (enteredDoorCode && passedRetinaScan) || hasDoorKey || knowsOverridePassword {print("Welcome!") } else {print("ACCESS DENIED") } // Prints "Welcome!"

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轉(zhuǎn)載于:https://www.cnblogs.com/wuhuacong/p/8134440.html

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