ios 如何在 Swift 3 中为我在 for 循环期间修改的数组编写 for 循环？
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How do I write a for-loop in Swift 3 for an array that I modify during the for loop?
提问by QuantumHoneybees
So, I have a for-loop that looks similar to this:
所以，我有一个与此类似的 for 循环：
for var i = 0; i < results.count ; i += 1 {
if (results[i] < 5) {
results.removeAtIndex(i)
i -= 1
}
}
This used to work. But when I changed it to the preferred Swift 3.0 syntax:
这曾经奏效。但是当我将其更改为首选的 Swift 3.0 语法时：
for var i in 0..<results.count {
if (results[i] < 5) {
results.removeAtIndex(i)
i -= 1
}
}
I get an array IOOBE exception because it doesn't re-check the count and continues on until the original results.count.
我收到一个数组 IOOBE 异常，因为它不会重新检查计数并继续直到原始results.count.
How do I fix this? It works now, but I don't want to get into trouble in the future.
我该如何解决？它现在有效，但我不想在将来惹上麻烦。
回答by Unheilig
While the solution making use of filteris a fine solution and it's more Swift-ly, there is another way, if making use of for-inis, nonetheless, still desired:
虽然使用 of 的解决方案filter是一个很好的解决方案，而且它更Swift-ly，但还有另一种方法，如果使用 offor-in仍然需要：
var results = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for var i in (0..<results.count).reverse()
{
if (results[i] < 5)
{
results.removeAtIndex(i)
//i -= 1
}
}
print(results)
Result:
结果：
[5, 6, 7, 8, 9, 10]
We could omit this line i -= 1altogether, in addition.
此外，我们可以i -= 1完全省略这一行。
The problem with removeAtIndexwithin the loop is that it will not cause the array to re-index itself in-placeand thus causing an array out of bounds exception due to countnot being updated.
removeAtIndex循环内的问题在于它不会导致数组就地重新索引自身，从而导致由于count未更新而导致数组越界异常。
By traversing backwards, the out of bounds exception can thus be avoided.
通过向后遍历，可以避免越界异常。
回答by Brandon Shega
Could you use a filterinstead?
你可以用 afilter代替吗？
let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let greaterThan5 = numbers.filter{for (index, element) in results.enumerate() {
if (element < 5) {
results.removeAtIndex(index)
}
}
>= 5}
print(greaterThan5)
回答by Luka Jacobowitz
If you want to continue using a for-loop, you can enumerate over both index and element using enumerate:
如果要继续使用for-loop，可以使用以下方法枚举索引和元素enumerate：
for var i in (0..<results.count) where results.indices.contains(i) {
//if the index doesn't exist, the loop will be stopped.
if (results[i] < 5) {
results.removeAtIndex(i)
}
}
Although depending on what you're doing in your loop, the filtermethod might be a better idea.
尽管取决于您在循环中做什么，该filter方法可能是一个更好的主意。
回答by Miguel Herrero
If your loop goes forward...
如果你的循环继续......
##代码##