iphone - 在 UITableView 中创建运行总和

Question

我有一个填充了事务的 UITableView(之前通过导航栏中的按钮保存)。每行有五个 UILabel:日期、描述、人员、值(存款和取款)余额。该表按日期排序。如何获得每日余额？余额是从第一个输入到当前行的总和(+ 和 -)。

我有以下代码 (JournalDetail.m)，但我只得到与值相同的金额，而不是累计金额(余额)

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *CellIdentifier = @"Cell";
GxPolizasL *cell = (GxPolizasL *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:@"GxPolizasL" owner:self options:nil];
cell = gxPolizasL;
self.gxPolizasL = nil;
GMDiario *gmDiarioy = (GMDiario *)[self.fetchedResultsController objectAtIndexPath:indexPath];
//Date value
NSDateFormatter* df = [[NSDateFormatter alloc] init];
[df setDateFormat:@"dd/MM/yy"];
cell.fechao.text = [df stringFromDate:gmDiarioy.pzFecha];
[df release];
//Description value
cell.referencia.text=gmDiarioy.pzAlias;
//Person value
cell.item.text = gmDiarioy.persona.prAlias;
//Transaction value
NSNumberFormatter* vf = [[NSNumberFormatter alloc] init];    
[vf setNumberStyle:NSNumberFormatterCurrencyStyle];
cell.valuem.text= [vf stringFromNumber: gmDiarioy.pzMont01];
[vf release];
//This is where the balance value is intended to be created
NSDecimalNumber *saldoAc = [NSDecimalNumber decimalNumberWithString:@"0.0"];
NSDecimalNumber *objectExpenseNumber = [gmDiarioy valueForKeyPath:@"pzMont01"];
saldoAc = [saldoAc decimalNumberByAdding:objectExpenseNumber];
NSLog(@"saldoAc: %@",saldoAc);
NSNumberFormatter* af = [[NSNumberFormatter alloc] init];
[af setNumberStyle:NSNumberFormatterCurrencyStyle];
cell.valuea.text= [af stringFromNumber: saldoAc];
[af release];
}
return cell;}

你能帮我弄清楚实现余额值的正确方法是什么吗？提前致谢。非常感谢您的帮助。

这是 self.fetchedResultsController 的代码

- (NSFetchedResultsController *)fetchedResultsController
{
if (__fetchedResultsController != nil) {
return __fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];

//Diario is an entity that keeps all transactions
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Diario" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];    

//This is to select only the journals for the current account (value passed at didSelectRowAtIndexPath from the previous UItableView
NSString *filtro=gmCuenta.cnAlias;  
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"cuenta.cnAlias like %@", filtro];
NSLog(@"NSPredicate1 %@", gmDiario.cuenta);
[fetchRequest setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"pzFecha" ascending:YES] autorelease];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil] autorelease];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();}
return __fetchedResultsController;
}

Answer 1

基本上您想要做的是:每次 cellForRowAtIndexPath: 被调用时，您想要遍历数据源数组并对从数组开头开始到以数组项等于相关单元格的行号(即 indexPath.row)。这将为您提供总计(余额)。

NSDecimalNumber *saldoAc = [NSDecimalNumber decimalNumberWithString:@"0.0"];
for (int i=0; i <= indexPath.row; i++) {
    NSIndexPath *indexPath = [NSIndexPath indexPathWithIndex:i];
    GMDiario *tempObj = (GMDiario *)[self.fetchedResultsController objectAtIndexPath:indexPath];
    NSDecimalNumber *objectExpenseNumber = [tempObj valueForKeyPath:@"pzMont01"];
    saldoAc = [saldoAc decimalNumberByAdding:objectExpenseNumber];
}
NSNumberFormatter* af = [[NSNumberFormatter alloc] init];
[af setNumberStyle:NSNumberFormatterCurrencyStyle];
cell.valuea.text= [af stringFromNumber: saldoAc];
[af release];

另一条评论 - 您应该在退出 if (cell == nil) block 后设置单元格 subview 的值。否则当你的 tableView 开始滚动时你会遇到麻烦。