我在一个部分中有一个实体显示在表视图中.实体有两个属性,即workoutName和trainingLevel.两者都是字符串类型.培训级别包括3种类型：1,2,3(trainingLevel =(整数16或字符串类型？哪个是理想的？)我想将表分为三个部分,每个部分包含相应培训级别的条目.
我该怎么做？我目前使用的代码如下：
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return self.workoutType.workouts.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell =
[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:CellIdentifier];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}
WorkoutSet *workoutSet = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.textLabel.text = workoutSet.workoutName;
cell.detailTextLabel.text = [NSString stringWithFormat:@"(%d)",workoutSet.days.count];
}
-(void)fetchWorkoutSets
{
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"WorkoutSet"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"workoutType = %@",self.workoutType];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"workoutName" ascending:YES];
[fetchRequest setSortDescriptors:@[sortDescriptor]];
[fetchRequest setPredicate:predicate];
self.fetchedResultsController = [[NSFetchedResultsController alloc]
initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil cacheName:nil];
NSError *error;
if (![self.fetchedResultsController performFetch:&error])
{
NSLog(@"Fetch Failed: %@",error);
}
}
我正在努力的是：
>如何通过核心数据模型确定每个部分的行数,方法是获取训练级别为1或2或3的条目数.
>如何通过获取正确的项目来填充每个部分的行.
>如何给每个段头标题.
解决方法
以下是使用fetchedResultsController的一个很好的教程：
http://www.raywenderlich.com/999/core-data-tutorial-for-ios-how-to-use-nsfetchedresultscontroller
@property (nonatomic,strong)NSManagedObjectContext* managedObjectContext; @property (nonatomic,retain)NSFetchedResultsController *fetchedResultsController;
在您的fetchedResultsController属性中,使用sectionKeyNamePath在部分中设置获取的结果：
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:@"Workouts"
inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"workoutName" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:managedObjectContext
sectionNameKeyPath:@"trainingLevel"
cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
您的fetchedResultsController的初始人数可能发生在您的-viewDidLoad中：
- (void)viewDidLoad {
[super viewDidLoad];
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
// Update to handle the error appropriately.
NSLog(@"Unresolved error %@,%@",error,[error userInfo]);
exit(-1); // Fail
}
}
然后,您将返回以下部分的行数和行数：
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [[self.fetchedResultsController sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
{
id <NSFetchedResultsSectionInfo> sectionInfo =
[[[self fetchedResultsController] sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
然后,您可以获取特定行的托管对象,如下所示：
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// init the cell
// and whatever other setup needed
WorkoutSet *workoutSet =
[self.fetchedResultsController objectAtIndexPath:indexPath];
// configure the cell from the managedObject properties
}
