CGVector Extension

向量的大小、求和、正规化等

extension CGVector {
    
    /// 向量的大小
    var length: Double {
        get {
            let dx = Double(self.dx)
            let dy = Double(self.dy)
            return sqrt(dx * dx + dy * dy)
        }
    }
    
    /// Normalizing
    var normalizer: CGVector {
        get {
            return self / length
        }
    }
    
    var angle: Double {
        get {
            return atan2(Double(dy), Double(dx))
        }
    }
    
    /// 向量加法
    ///
    /// - Parameters:
    ///   - left: One Vector
    ///   - right: Other Vector
    /// - Returns: 向量的和
    static func +(left: CGVector, right: CGVector) -> CGVector {
        return CGVector(dx: left.dx + right.dx, dy: left.dy + right.dy)
    }
    
    static func +=(left: inout CGVector, right: CGVector) {
        left = left + right
    }
    
    static func *(vector: CGVector, scalar: Double) -> CGVector {
        return CGVector(dx: Double(vector.dx) * scalar, dy: Double(vector.dy) * scalar)
    }
    
    static func *(scalar: Double, vector: CGVector) -> CGVector {
        return CGVector(dx: Double(vector.dx) * scalar, dy: Double(vector.dy) * scalar)
    }
    
    static func *= (vector: inout CGVector, scalar: Double) {
        vector = vector * scalar
    }
    
    static func -(left: CGVector, right: CGVector) -> CGVector {
        return CGVector(dx: left.dx - right.dx, dy: left.dy - right.dy)
    }
    
    static func -= (left: inout CGVector, right: CGVector) {
        left = left - right
    }
    
    static func /(left: CGVector, scalar: Double) -> CGVector {
        return CGVector(dx: Double(left.dx) / scalar, dy: Double(left.dy) / scalar)
    }
    
    static func /= (vector: inout CGVector, scalar: Double) {
        vector = vector / scalar
    }
}

/*
//如果不写在最外层而是写在类里面，要写成static
func +(left: CGVector, right: CGVector) -> CGVector {
    return CGVector(dx: left.dx + right.dx, dy: left.dy + right.dy)
}
*/