objective-c - 对从 coreData 检索到的值求和并在部分中显示

Question

我想在给定部分中添加所有金额标签，并在部分标题中显示总数。我的表格 View 看起来像这样。

章节标题 - 12/07/2012

categoryName  Amount
 Groceries     100
  Social       100

章节标题 - 2012 年 10 月 4 日

categoryName  Amount
  Gas          500
  Social       600

现在我想在第一节标题中显示总数 200，在下一个标题中显示 1100

-(IBAction)bydate:(id)sender
{
[self.expenseArray removeAllObjects];
[self.expenseArrayCount removeAllObjects];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];

for(NSManagedObject *records in self.listOfExpenses){
    NSString *compareDates = [dateFormatter stringFromDate:[records valueForKey:@"date"]];
    BOOL isAvail = NO;
    for (int i = 0; i<[self.expenseArray count]; i++){
        if([compareDates isEqualToString:[self.expenseArray objectAtIndex:i]])
            isAvail = YES;
    }
    if(!isAvail)
        [self.expenseArray addObject:compareDates];
}
int count = 0;
for (int i = 0 ; i < [self.expenseArray count] ; i ++){
    NSString *compareDates = [self.expenseArray objectAtIndex:i];
    for(NSManagedObject *info in self.listOfExpenses){
        if([compareDates isEqualToString:[dateFormatter stringFromDate:[info valueForKey:@"date"]]])
            count++;
    }
    [self.expenseArrayCount addObject:[NSNumber numberWithInt:count]];
    count = 0;
}
[self.byDateTab reloadData];
[dateFormatter release];
}

 -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
   //not posting un necessary code.

    else if (tableView == self.byDateTab)
{
    for(int i = 0; i < [self.expenseArrayCount count];i++)
    {
        if(indexPath.section == 0)
        {
            NSManagedObject *records = nil;
            records = [self.listOfExpenses objectAtIndex:indexPath.row];
            self.firstLabel.text = [records valueForKey:@"category"];
            self.secondLabel.text = [records valueForKey:@"details"];
            NSString *amountString = [NSString stringWithFormat:@"%@",[records valueForKey:@"amount"]];
            self.thirdLabel.text = amountString;
        }
        else if (indexPath.section == i)
        {
            int rowCount = 0;
            for(int j=0; j<indexPath.section; j++)
            {
                rowCount = rowCount + [[self.expenseArrayCount objectAtIndex:j]intValue];
            }
            NSManagedObject *records = nil;
            records = [self.listOfExpenses objectAtIndex:(indexPath.row + rowCount) ];
            self.firstLabel.text = [records valueForKey:@"category"];
            self.secondLabel.text = [records valueForKey:@"details"];
            NSString *amountString = [NSString stringWithFormat:@"%@",[records valueForKey:@"amount"]];
            self.thirdLabel.text = amountString;

        }
    }
}


-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
NSString *title = [[[NSString alloc]init]autorelease];
if(tableView == self.byDateTab)
    title =  [self.expenseArray objectAtIndex:section];
return title;
}

-(UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
UIView *headerView = [[[UIView alloc]init] autorelease];
if(tableView == self.byDateTab){
    headerView.frame = CGRectMake(310, 0, tableView.bounds.size.width, 30);
    [headerView setBackgroundColor:[UIColor colorWithRed:149.0/255 green:163.0/255 blue:173.0/255 alpha:1]];
    UILabel *leftLabel = [[[UILabel alloc]initWithFrame:CGRectMake(10, 3, tableView.bounds.size.width-10, 18)]autorelease];
    leftLabel.text = [self tableView:tableView titleForHeaderInSection:section];
    leftLabel.textColor = [UIColor whiteColor];
    leftLabel.font = [UIFont fontWithName:@"AmericanTypewriter" size:17.0];
    leftLabel.backgroundColor = [UIColor clearColor];
    [headerView addSubview:leftLabel];

    NSNumberFormatter *formatter = [[NSNumberFormatter alloc]init];
    NSString *a = [formatter currencySymbol];

    UILabel *rightLabel = [[[UILabel alloc]initWithFrame:CGRectMake(250, 3, tableView.bounds.size.width-10, 18)]autorelease];
    rightLabel.text = [NSString stringWithFormat:@"(%@)",a];
    rightLabel.textColor = [UIColor whiteColor];
    rightLabel.font = [UIFont fontWithName:@"AmericanTypewriter" size:17.0];
    rightLabel.backgroundColor = [UIColor clearColor];
    [headerView addSubview:rightLabel];



}

Answer 1

你需要实现这个方法:
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
它返回给定部分的标题。因此，您需要找出哪些记录与节号匹配，并遍历记录以计算总数。
您可能需要考虑在上述方法之外执行此操作，以便在每次调用此方法时不计算每个部分的总金额。
您可以在加载数据后立即创建一组“预计算”标题，并且只执行以下操作:

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section  
{  
    return [titles objectAtIndex:section];  
}