ios - 最初使用非零值调用的 numberOfRowsInSection

Question

当第一次调用以下数据源时

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return self.firstFetchedResultController.sections.count + self.secondFetchedResultController.sections.count;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    NSInteger rowsCount = 0;
    NSLog(@"Section : %ld", (long)section);

    //First result controller
    if (section < [self.secondFetchedResultController.sections count]) {
        id  sectionInfo = [self.firstFetchedResultController sections][section];
        rowsCount = [sectionInfo numberOfObjects];
    } else {    //Second result controller
        id  sectionInfo = [self.secondFetchedResultController sections][section];
        rowsCount = [sectionInfo numberOfObjects];
    }

    return rowsCount;
}

最初打印的部分值为 3。当它进入 numberOfRows 时，应用程序崩溃，因为循环会将进程带到 else block ，而我的 secondaryFetchedResultController 中没有第三部分。

仅供引用:我在当前 ViewController 中使用了两个 fetchedResultsController。我正面临崩溃，因为在这种情况下，第一个/第二个ViewController 对于第 3 节没有值(value)。

Answer 1

您需要将第一个 resultController 的计数减去该部分，以便拥有从 0 开始的索引:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    NSInteger rowsCount = 0;
    NSLog(@"Section : %ld", (long)section);

    // Let's save the count to a variable in order to have an answer more readable
    NSInteger firstSectionCount = [self.secondFetchedResultController.sections count];

    //First result controller
    if (section < firstSectionCount) {
        id  sectionInfo = [self.firstFetchedResultController sections][section];
        rowsCount = [sectionInfo numberOfObjects];
    } else {    //Second result controller
        // HERE, we subtract firstSectionCount to section.
        id  sectionInfo = [self.secondFetchedResultController sections][section - firstSectionCount];
        rowsCount = [sectionInfo numberOfObjects];
    }

    return rowsCount;
}