Question

如何更改代码，因为在swift 3中不推荐使用C style for statement？我在以下代码行中收到错误：

for var frame = 0; frame <= frameCount; frame += 1

func keyframePathsWithDuration(_ duration: CGFloat, lastUpdatedAngle: CGFloat, newAngle: CGFloat, radius: CGFloat, type: RMIndicatorType) -> [CGPath] {
    let frameCount: Int = Int(ceil(duration * 60))
    var array: [CGPath] = []
    for var frame = 0; frame <= frameCount; frame += 1 {
        let startAngle = degreeToRadian(-90)

        let angleChange = ((newAngle - lastUpdatedAngle) * CGFloat(frame))
        let endAngle = lastUpdatedAngle + (angleChange / CGFloat(frameCount))
        array.append((self.pathWithStartAngle(startAngle, endAngle: endAngle, radius: radius, type: type).cgPath))
    }
    return array
}

Answer 1

以下是如何将C风格的循环转换为快速循环。

如果C-style for循环采用以下形式：

for var i = x ; i < y ; i++ {

将其更改为：

for i in x..<y {

如果是这种形式：

for var i = x ; i <= y ; i++ {

将其更改为：

for i in x...y {

所以在你的情况下，它会变成：

for frame in 0...frameCount {

这是转型的更通用版本：

for var i = x ; i <operator> y ; i += z

为：

for i in stride(from: x, to/through: y, by: z)

Answer 2

尝试使用Swift 3/4的新语法

func keyframePathsWithDuration(_ duration: CGFloat, lastUpdatedAngle: CGFloat, newAngle: CGFloat, radius: CGFloat, type: RMIndicatorType) -> [CGPath] {
            let frameCount: Int = Int(ceil(duration * 60))
            var array: [CGPath] = []
            for frame in 0...frameCount {
                let startAngle = degreeToRadian(-90)

                let angleChange = ((newAngle - lastUpdatedAngle) * CGFloat(index))
                let endAngle = lastUpdatedAngle + (angleChange / CGFloat(frameCount))
                array.append((self.pathWithStartAngle(startAngle, endAngle: endAngle, radius: radius, type: type).cgPath))
            }
            return array
}

有关新循环语法的更多信息，请参阅：

https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ControlFlow.html

C语言for语句在swift 3中已弃用

2 个答案: