## 按位運算符 ### ~ 1變0，0變1。  ~~~ let initialBits: UInt8 = 0b00001111 let invertedBits = ~initialBits // equals 11110000 ~~~ ### $ 全1得1，其他為0  ~~~ let firstSixBits: UInt8 = 0b11111100 let lastSixBits: UInt8 = 0b00111111 let middleFourBits = firstSixBits & lastSixBits // equals 00111100 ~~~ ### | 有1得1，其他為0  ~~~ let someBits: UInt8 = 0b10110010 let moreBits: UInt8 = 0b01011110 let combinedbits = someBits | moreBits // equals 11111110 ~~~ ### ^ 相異為1，相同為0  ~~~ let firstBits: UInt8 = 0b00010100 let otherBits: UInt8 = 0b00000101 let outputBits = firstBits ^ otherBits // equals 00010001 ~~~ ### <<和>> <<整體左移，右邊填0； >> 整體右移，左邊填0。  ~~~ let shiftBits: UInt8 = 4 // 00000100 in binary shiftBits << 1 // 00001000 shiftBits << 2 // 00010000 shiftBits << 5 // 10000000 shiftBits << 6 // 00000000 shiftBits >> 2 // 00000001 ~~~ ## 算子函數 上面講解的都是簡單的運算符，下面的是為對象添加運算符，使之可計算。 ### 符號在中間 ~~~ struct Vector2D { var x = 0.0, y = 0.0 } func + (left: Vector2D, right: Vector2D) -> Vector2D { return Vector2D(x: left.x + right.x, y: left.y + right.y) } let vector = Vector2D(x: 3.0, y: 1.0) let anotherVector = Vector2D(x: 2.0, y: 4.0) let combinedVector = vector + anotherVector // combinedVector is a Vector2D instance with values of (5.0, 5.0) ~~~ ### 前綴和后綴 前綴關鍵字prefix 后綴關鍵字postfix ~~~ prefix func - (vector: Vector2D) -> Vector2D { return Vector2D(x: -vector.x, y: -vector.y) } let positive = Vector2D(x: 3.0, y: 4.0) let negative = -positive // negative is a Vector2D instance with values of (-3.0, -4.0) let alsoPositive = -negative // alsoPositive is a Vector2D instance with values of (3.0, 4.0) ~~~ ### 復合賦值運算符 這里用+=舉例。 ~~~ func += (inout left: Vector2D, right: Vector2D) { left = left + right } var original = Vector2D(x: 1.0, y: 2.0) let vectorToAdd = Vector2D(x: 3.0, y: 4.0) original += vectorToAdd // original now has values of (4.0, 6.0) ~~~ ## 其他 ### 參考資料 [The Swift Programming Language (Swift 2.1)](https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html) ### 文檔修改記錄 | 時間 | 描述 | |-----|-----| | 2015-11-1 | 根據 [The Swift Programming Language (Swift 2.1)](https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html)中的Classes and Structures總結 | 版權所有：[http://blog.csdn.net/y550918116j](http://blog.csdn.net/y550918116j)