“无法分配给”迭代遍历struct数组的错误 [英] "Cannot assign to" error iterating through array of struct

问题描述

我有一个结构数组：

struct CalendarDate {
    var date: NSDate?
    var selected = false
}

private var collectionData = [CalendarDate]()

我只想填写这样的日期：

Which I simply populate with a date like this:

    for _ in 1...7 {
        collectionData.append(CalendarDate(date: NSDate(), selected: false))
    }

所以当你点击一个collectionView时，我只想循环遍历数据并将它们全部标记为False。

So when you tap on a collectionView, I simply want to loop through the data and mark them all as False.

    for c in collectionData {
        c.selected = false  ///ERROR: Cannot assign to 'selected' in 'c'
    }

为什么我会收到此错误？

Why do I get this error?

如果我这样做，它可以正常工作但我想要要知道上面我做错了什么：

If I do this, it works fine but I want to know what I did wrong above:

    for i in 0..<collectionData.count {
        collectionData[i].selected = false
    }

推荐答案

据我所知，迭代器

for collection中的c

返回 collectionData <中的项目副本/ code> - （ structs 是值类型，而不是引用类型，请参阅 http://www.objc.io/issue-16/swift-classes-vs-structs.html ），而迭代

returns copies of the items in collectionData - (structs are value types, not reference types, see http://www.objc.io/issue-16/swift-classes-vs-structs.html), whereas the iteration

for i in 0 ..< collectionData.count

访问实际值。如果我是正确的，那么分配给迭代器返回的 c 是没有意义的......它没有指向原始值，而

accesses the actual values. If I am right in that, it is pointless to assign to the c returned from the iterator... it does not "point" at the original value, whereas the

collectionData [i] .selected = false

in迭代是原始值。

其他一些评论员建议

for collectionData <（var c） / code>

for (var c) in collectionData

虽然这允许你分配到 c ，但它仍然是一个副本，不是指向原始的指针，虽然您可以修改 c ，但 collectionData 仍然保持不变。

but although this allows you to assign to c, it is still a copy, not a pointer to the original, and though you can modify c, collectionData remains untouched.

答案是：A）使用最初记录的迭代或B）将数据类型更改为类，而不是结构。

The answer is either A) use the iteration as you originally noted or B) change the data type to a class, rather than a struct.

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