删除部分中的最后一个单元格后，iOS 应用程序崩溃 [英] iOS app crashes after deleting the last cell in section

问题描述

所以每次我尝试删除该部分的最后一个单元格时，我的应用都会崩溃.

So I've my app crashing everytime I try to delete the last cell of the section.

例如，如果我的部分有 10 行，我可以毫无问题地删除它们，但最后一个会引发以下错误:

Ex., if my section has 10 rows, I can delete them without any problem but the last one throws the following error:

由于未捕获的异常NSInternalInconsistencyException"而终止应用程序，原因:无效更新:节数无效.更新后表视图中包含的节数(1)必须等于更新前表视图中包含的节数(3)，加上或减去插入或删除的节数(0插入，0已删除).'

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of sections. The number of sections contained in the table view after the update (1) must be equal to the number of sections contained in the table view before the update (3), plus or minus the number of sections inserted or deleted (0 inserted, 0 deleted).'

我已经在这里搜索并找到了一些解决此问题的方法，但我尝试了所有方法并无法解决此问题，它仍然崩溃并抛出相同的错误.

I've searched around here and found some ways to fix this problem, but I tried them all and couldn't get this issue fixed, it still crashes and throws the same error.

我的代码的相关部分如下:

The related parts of my code goes as it follows:

override func numberOfSections(in tableView: UITableView) -> Int {
    if (main_arr.count > 0 && sub_arr.count > 0) {
        self.numberOfSections = 3
    } else {
        self.numberOfSections = 2
    }

    return self.numberOfSections
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if (section == 0) {
        return 1
    } else if (section == 1 && main_arr.count > 0) {
        return main_arr.count
    } else {
        return sub_arr.count
    }

}

override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
    return true
}

// Override to support editing the table view.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {

        switch indexPath.section {

        case 1:
            main_arr.remove(at: indexPath.row)

        case 2:
            sub_arr.remove(at: indexPath.row)

        default:
            print("default 001")
        }

        tableView.deleteRows(at: [indexPath], with: .fade)

    } else if editingStyle == .insert {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }
}

编辑 1

我尝试处理负责 numberOfSections 的全局变量，因此当我的任何一个 arrays.count == 0 时，它将减 1，但它没有解决问题.

I tried to handle the global variable, responsible for the numberOfSections so when any of my arrays.count == 0 it will be decreased by 1, but it didn't solved the issue.

我确实完全理解错误消息，例如，如果我有 3 个部分，并且我删除了其中一个部分的全部内容，我应该删除一个部分并将其也从数据源中删除.

I do understand completely the error message, like, if I've 3 sections, and I delete the whole content of one of them, I should delete one section and delete it from the datasource as well.

推荐答案

问题是numberOfSections在你删除行之前和之后返回不同的值，但是你并没有删除任何部分.因此，除了 deleteRows

The problem is that numberOfSections returns different values before and after you delete rows, but you don't delete any sections. So you should either return a constant value in numberOfSections or call deleteSections in addition to deleteRows

要记住的主要内容如下:

The main thing to remember is the following:

UITableView 必须始终包含与数据源相同数量的行和部分.

您不能只在 numberOfSections 或 numberOfRows 数据源方法中返回一个新值.每次更改都应使用删除/插入行(节)方法进行补偿.反之亦然:如果删除/插入 tableView，则必须在 dataSource 方法中返回相应的值.正如您的异常消息所述:

You cannot just return a new value in numberOfSections or numberOfRows dataSource methods. Every change should be compensated with delete/insert rows(sections) method. And vice versa: if you delete/insert to tableView, you must return corresponding values in dataSource methods. Just as your exception message states:

表视图中包含的节数更新后(1) 必须等于表中包含的节数查看更新前(3)，加减版块数插入或删除(插入 0 个，删除 0 个).

The number of sections contained in the table view after the update (1) must be equal to the number of sections contained in the table view before the update (3), plus or minus the number of sections inserted or deleted (0 inserted, 0 deleted).

因为3+0≠1.在这种情况下，您应该删除两个部分以避免崩溃.

It's because 3+0≠1. In this case you should have deleted two sections to avoid crash.

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