ios 如何删除 Swift 数组中的所有 nil 元素？
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How can I remove all nil elements in a Swift array?
提问by TIMEX
Basic way doesn't work.
基本方法不起作用。
for index in 0 ..< list.count {
if list[index] == nil {
list.removeAtIndex(index) //this will cause array index out of range
}
}
回答by zneak
The problem with your code is that 0 ..< list.countis executed once at the beginning of the loop, when liststill has all of its elements. Each time you remove one element, list.countis decremented, but the iteration range is not modified. You end up reading too far.
您的代码的问题是0 ..< list.count在循环开始时执行一次，此时list仍然具有其所有元素。每次删除一个元素，list.count递减，但迭代范围不修改。你最终读得太远了。
In Swift 4.1 and above, you can use compactMapto discard the nilelements of a sequence. compactMapreturns an array of non-optional values.
在 Swift 4.1 及更高版本中，您可以使用compactMap丢弃nil序列的元素。compactMap返回一组非可选值。
let list: [Foo?] = ...
let nonNilElements = list.compactMap { list = list.filter { list.flatMap { list.compactMap{ ##代码## }
}
!= nil }
}
If you still want an array of optionals, you can use filterto remove nilelements:
如果你仍然想要一个可选的数组，你可以使用filter删除nil元素：
回答by Marcel Molina
In Swift 2.0 you can use flatMap:
在 Swift 2.0 中你可以使用 flatMap：
##代码##回答by kalafun
Now in swift 4.2 you can use
现在在 swift 4.2 中你可以使用
##代码##- list.flatMap { $0 } is already deprecated.
- list.flatMap { $0 } 已被弃用。
