ios Swift 中的 MIN() 和 MAX() 并将 Int 转换为 CGFloat
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MIN() and MAX() in Swift and converting Int to CGFloat
提问by fulvio
I'm getting some errors with the following methods:
我在使用以下方法时遇到一些错误：
1) How do I return screenHeight / cellCountas a CGFLoatfor the first method?
1）我如何return screenHeight / cellCount作为CGFLoat第一种方法？
2) How do I use the equivalent of ObjC's MIN() and MAX() in the second method?
2) 如何在第二种方法中使用等效的 ObjC 的 MIN() 和 MAX()？
func tableView(tableView: UITableView!, heightForRowAtIndexPath indexPath: NSIndexPath!) -> CGFloat {
var cellCount = Int(self.tableView.numberOfRowsInSection(indexPath.section))
return screenHeight / cellCount as CGFloat
}
// #pragma mark - UIScrollViewDelegate
func scrollViewDidScroll(scrollView: UIScrollView) {
let height = CGFloat(scrollView.bounds.size.height)
let position = CGFloat(MAX(scrollView.contentOffset.y, 0.0))
let percent = CGFloat(MIN(position / height, 1.0))
blurredImageView.alpha = percent
}
回答by Mick MacCallum
1: You can't downcast from Int to CGFloat. You have to initialize a CGFloat with the Int as input.
1：你不能从 Int 向下转型到 CGFloat。您必须使用 Int 作为输入初始化 CGFloat。
return CGFloat(screenHeight) / CGFloat(cellCount)
2: Use the min and max functions defined by the standard library. They're defined as follows:
2：使用标准库定义的min和max函数。它们的定义如下：
func min<T : Comparable>(x: T, y: T, rest: T...) -> T
func max<T : Comparable>(x: T, y: T, rest: T...) -> T
Usage is as follows.
用法如下。
let lower = min(17, 42) // 17
let upper = max(17, 42) // 42
回答by Alan Zeino
If you're using Swift 3, max()and min()are now called on the sequence (i.e., collection) instead of passing in arguments:
如果您使用的是 Swift 3，max()并且min()现在在序列（即集合）上调用而不是传入参数：
let heights = [5, 6]
let max = heights.max() // -> 6
let min = heights.min() // -> 5
let heights = [5, 6]
let max = heights.max() // -> 6
let min = heights.min() // -> 5
回答by Greg
You need to explicitly convert cellCountto CGFloat, since Swift doesn't do automatic type conversion between integers and floats:
您需要显式转换cellCount为CGFloat，因为 Swift 不会在整数和浮点数之间进行自动类型转换：
return screenHeight / CGFloat(cellCount)
minand maxfunctions are defined by the standard library.
min和max函数由标准库定义。
回答by Grimxn
You can just use min() and max() - they're built-in.
您可以只使用 min() 和 max() - 它们是内置的。
If you wanted to roll your own (why? - maybe to extend it) you would use something like
如果你想推出自己的（为什么？ - 也许是扩展它），你会使用类似的东西
func myMin <T : Comparable> (a: T, b: T) -> T {
if a > b {
return b
}
return a
}
