Question

在我在swift项目中使用的一个库中，一行会导致应用程序崩溃。我试着理解并解决它，但没有运气。我知道它是由数组索引错误引起的。有人可以帮忙吗？

崩溃报告

Fatal Exception: NSRangeException
0  CoreFoundation                 0x180a42e38 __exceptionPreprocess
1  libobjc.A.dylib                0x1800a7f80 objc_exception_throw
2  CoreFoundation                 0x180922ebc -[__NSArrayM removeObjectAtIndex:]
3                          0x10000ac70 -[ChatSectionManager messageForIndexPath:] (ChatSectionManager.m:435)
4                          0x10001c194 -[Chat tableView:cellForRowAtIndexPath:] (Chat.m:596)
5  UIKit                          0x185ee2f40 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:]
6  UIKit                          0x185ee30a8 -[UITableView _createPreparedCellForGlobalRow:willDisplay:]

ChatSectionManager.m

 - (QBChatMessage *)messageForIndexPath:(NSIndexPath *)indexPath {

    if (indexPath.item == NSNotFound) {
        return nil;
    }

    QMChatSection *currentSection = self.chatSections[indexPath.section];
    //crashes here line 435
    return currentSection.messages[indexPath.item];
}

Chat.m

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [self.chatSectionManager messagesCountForSectionAtIndex:section];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return self.chatSectionManager.chatSectionsCount;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *) indexPath {

    QBChatMessage *messageItem = [self.chatSectionManager messageForIndexPath:indexPath];

... 包含 removeObjectAtIndex

的方法

- (void)deleteMessages:(NSArray *)messages animated:(BOOL)animated {

    dispatch_async(_serialQueue, ^{

        NSMutableArray *messagesIDs = [NSMutableArray array];
        NSMutableArray *itemsIndexPaths = [NSMutableArray array];
        NSMutableIndexSet *sectionsIndexSet = [NSMutableIndexSet indexSet];

        self.editableSections = self.chatSections.mutableCopy;

        for (QBChatMessage *message in messages) {
            NSIndexPath *indexPath = [self indexPathForMessage:message];
            if (indexPath == nil) continue;

            QMChatSection *chatSection = self.chatSections[indexPath.section];
            [chatSection.messages removeObjectAtIndex:indexPath.item];

            if (chatSection.isEmpty) {
                [sectionsIndexSet addIndex:indexPath.section];
                [self.editableSections removeObjectAtIndex:indexPath.section];

                // no need to remove elements whose section will be removed
                NSArray *items = [itemsIndexPaths copy];
                for (NSIndexPath *index in items) {
                    if (index.section == indexPath.section) {
                        [itemsIndexPaths removeObject:index];
                    }
                }
            } else {

                [itemsIndexPaths addObject:indexPath];
            }
        }

        dispatch_sync(dispatch_get_main_queue(), ^{

            self.chatSections = self.editableSections.copy;
            self.editableSections = nil;

            if ([self.delegate respondsToSelector:@selector(chatSectionManager:didDeleteMessagesWithIDs:atIndexPaths:withSectionsIndexSet:animated:)]) {

                [self.delegate chatSectionManager:self didDeleteMessagesWithIDs:messagesIDs atIndexPaths:itemsIndexPaths withSectionsIndexSet:sectionsIndexSet animated:animated];
            }
        });
    });
}

注意：此次崩溃是随机发生的，我不知道为什么

FABRIC CRASH REPORT http://crashes.to/s/679e90f0c90

Answer 1

这绝对是deleteMessages的问题，看看你的主题16在崩溃的地方：

QMChatSectionManager.m第228行 __48- [QMChatSectionManager deleteMessages：animated：] _ block_invoke

检查哪条线228确切地知道问题是什么，但是我会在这里走出去并猜测它

[chatSection.messages removeObjectAtIndex:indexPath.item];

所以你要在线程16上删除messageForIndexPath主线程上引用的数据结构。正如您所注意到的，这是对竞争条件的公开邀请，几乎不可能按需复制。

修复方法是不修改后台线程中chatSection的内容。看起来你已经有了正确的想法，你在主线程上分配完成的部分列表，

self.chatSections = self.editableSections.copy;

将该逻辑应用于部分列表中更改的每个项目，随机崩溃将消失。

致命异常：NSRangeException - 超出边界的索引2 [0 .. 1]

1 个答案: