swift2 运算符函数

概述运算符函数 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, 运算符函数

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 是一个新的Vector2D,值为 (5.0,5.0)

前置或后置运算符 函数前标注 prefix或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 为 (-3.0,-4.0)let alsoPositive = -negative// alsoPositive 为 (3.0,4.0)

组合赋值表达式

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 现在为 (4.0,6.0)

prefix func ++ (inout vector: Vector2D) -> Vector2D {    vector += Vector2D(x: 1.0,y: 1.0)    return vector}var toIncrement = Vector2D(x: 3.0,y: 4.0)let afterIncrement = ++toIncrement// toIncrement 现在是 (4.0,5.0)// afterIncrement 现在也是 (4.0,5.0)

比较运算符

func == (left: Vector2D,right: Vector2D) -> Bool {    return (left.x == right.x) && (left.y == right.y)}func != (left: Vector2D,right: Vector2D) -> Bool {    return !(left == right)}let twoThree = Vector2D(x: 2.0,y: 3.0)let anotherTwoThree = Vector2D(x: 2.0,y: 3.0)if twoThree == anotherTwoThree {    print("这两个向量是相等的.")}

自定义运算符

prefix operator +++ {}prefix func +++ (inout vector: Vector2D) -> Vector2D {    vector += vector    return vector}var tobedoubled = Vector2D(x: 1.0,y: 4.0)let afterDoubling = +++tobedoubled// tobedoubled 现在是 (2.0,8.0)// afterDoubling 现在也是 (2.0,8.0)

在自定义运算符中还可以设定自定义运算符的优先级和结合性，来处理更复杂的任务。 总结

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