如何使用核心数据实现表格部分
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【中文标题】如何使用核心数据实现表格部分【英文标题】:How to implement table sections with core data 【发布时间】:2013-11-27 17:25:32 【问题描述】:我在我的 ios 应用程序中使用核心数据。我有一个表格视图来显示来自名为人员的实体的数据。实体persons有几个属性,其中一个是“日期”。我想在表格视图中创建 5 个永久部分(0.Today、1.Tomorrow、2.This week、3.This month、4.Upcoming),然后我希望根据每个部分显示数据日期。 我一直在寻找这个问题,但没有发现可以应用于我的应用程序。 恳请您告诉我正确的处理方法。
这是我目前的代码:
#import "PersonsTVC.h"
#import "Person.h"
@implementation PersonsTVC
@synthesize fetchedResultsController = __fetchedResultsController;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize selectedPerson;
@synthesize searchResults,titulosseccion;
- (void)setupFetchedResultsController
// 1 - Decide what Entity you want
NSString *entityName = @"Person"; // Put your entity name here
NSLog(@"Setting up a Fetched Results Controller for the Entity named %@", entityName);
// 2 - Request that Entity
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:entityName];
// 3 - Filter it if you want
//request.predicate = [NSPredicate predicateWithFormat:@"Person.name = Blah"];
// 4 - Sort it if you want
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"firstname"
ascending:YES
selector:@selector(localizedCaseInsensitiveCompare:)]];
// 5 - Fetch it
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
[self performFetch];
- (void) viewDidLoad
self.searchResults = [NSMutableArray arrayWithCapacity:[[self.fetchedResultsController fetchedObjects] count]];
[self.tableView reloadData];
-(void) viewDidUnload
self.searchResults = nil;
- (void)viewWillAppear:(BOOL)animated
[super viewWillAppear:animated];
[self setupFetchedResultsController];
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
return [[self.fetchedResultsController sections] count];
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
// Perform segue to detail when a SEARCH table cell is touched
if(tableView == self.searchDisplayController.searchResultsTableView)
[self performSegueWithIdentifier:@"Person Detail Segue" sender:tableView];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
static NSString *CellIdentifier = @"Persons Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
// Configure the cell...
// Configure the cell...
Person *person = nil;
if (tableView == self.searchDisplayController.searchResultsTableView)
NSLog(@"Configuring cell to show search results");
person = [self.searchResults objectAtIndex:indexPath.row];
else
NSLog(@"Configuring cell to show normal data");
person = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSString *fullname = [NSString stringWithFormat:@"%@ %@", person.firstname, person.surname];
cell.textLabel.text = person.firstname;
if ([person.inRole.color isEqual :@"Yellow"])
cell.imageView.image = [UIImage imageNamed:@"Yellow"];
if ([person.inRole.color isEqual :@"Black"])
cell.imageView.image = [UIImage imageNamed:@"Black"];
if ([person.inRole.color isEqual :@"Grey"])
cell.imageView.image = [UIImage imageNamed:@"Grey"];
if ([person.inRole.color isEqual :@"Red"])
cell.imageView.image = [UIImage imageNamed:@"Red"];
if ([person.inRole.color isEqual :@"Blue"])
cell.imageView.image = [UIImage imageNamed:@"Blue"];
if ([person.inRole.color isEqual :@"Dark Green"])
cell.imageView.image = [UIImage imageNamed:@"DarkGreen"];
if ([person.inRole.color isEqual :@"Light Green"])
cell.imageView.image = [UIImage imageNamed:@"LightGreen"];
if ([person.inRole.color isEqual :@"Light Blue"])
cell.imageView.image = [UIImage imageNamed:@"LightBlue"];
if ([person.inRole.color isEqual :@"Brown"])
cell.imageView.image = [UIImage imageNamed:@"Brown"];
if ([person.inRole.color isEqual :@"Dark Orange"])
cell.imageView.image = [UIImage imageNamed:@"DarkOrange"];
NSDate *fechasinformat = person.date;
NSString *fecha0 = [NSString stringWithFormat:@"%@", fechasinformat];
cell.detailTextLabel.text = fecha0;
return cell;
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
if (tableView == self.searchDisplayController.searchResultsTableView)
return [self.searchResults count];
else
return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
if (editingStyle == UITableViewCellEditingStyleDelete)
[self.tableView beginUpdates]; // Avoid NSInternalInconsistencyException
// Delete the person object that was swiped
Person *personToDelete = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(@"Deleting (%@)", personToDelete.firstname);
[self.managedObjectContext deleteObject:personToDelete];
[self.managedObjectContext save:nil];
// Delete the (now empty) row on the table
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self performFetch];
[self.tableView endUpdates];
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
if ([segue.identifier isEqualToString:@"Add Person Segue"])
NSLog(@"Setting PersonsTVC as a delegate of PersonDetailTVC");
PersonDetailTVC *personDetailTVC = segue.destinationViewController;
personDetailTVC.delegate = self;
NSLog(@"Creating a new person and passing it to PersonDetailTVC");
Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person"
inManagedObjectContext:self.managedObjectContext];
personDetailTVC.person = newPerson;
else if ([segue.identifier isEqualToString:@"Person Detail Segue"])
NSLog(@"Setting PersonsTVC as a delegate of PersonDetailTVC");
PersonDetailTVC *personDetailTVC = segue.destinationViewController;
personDetailTVC.delegate = self;
// Store selected Person in selectedPerson property
if(sender == self.searchDisplayController.searchResultsTableView)
NSIndexPath *indexPath = [self.searchDisplayController.searchResultsTableView indexPathForSelectedRow];
self.selectedPerson = [self.searchResults objectAtIndex:[indexPath row]];
else
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
self.selectedPerson = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(@"Passing selected person (%@) to PersonDetailTVC", self.selectedPerson.firstname);
personDetailTVC.person = self.selectedPerson;
else
NSLog(@"Unidentified Segue Attempted!");
- (void)theSaveButtonOnThePersonDetailTVCWasTapped:(PersonDetailTVC *)controller
// do something here like refreshing the table or whatever
// close the delegated view
[controller.navigationController popViewControllerAnimated:YES];
#pragma mark -
#pragma mark Content Filtering
-(void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
self.searchResults = [[self.fetchedResultsController fetchedObjects] filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings)
Person* person = evaluatedObject;
NSString* firstName = person.firstname;
//searchText having length < 3 should not be considered
if (!!searchText && [searchText length] < 3)
return YES;
if ([scope isEqualToString:@"All"] || [firstName isEqualToString:scope])
return ([firstName rangeOfString:searchText].location != NSNotFound);
return NO; //if nothing matches
]];
#pragma mark -
#pragma mark UISearchDisplayController Delegate Methods
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
[self filterContentForSearchText:searchString scope:@"All"];
return YES;
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption
[self filterContentForSearchText:[self.searchDisplayController.searchBar text] scope:@"All"];
return YES;
@end
【问题讨论】:
【参考方案1】:您将不得不大致执行以下操作:
将date
属性上的第一个排序描述符添加到获取请求。
向 Person 实体添加 transient 属性“sectionIdentifier”,
并实现自定义 getter - (NSString *)sectionIdentifier
到 Person
托管对象子类,它返回
“0”、“1”、“2”、“3”或“4”,具体取决于对象的date
属性。
在获取结果控制器的创建中设置sectionNameKeyPath:@"sectionIdentifier"
。
向表视图控制器添加一个titleForHeaderInSection
方法,即
根据部分返回“今天”、“明天”、...。
Apple 开发者库中的 DateSectionTitles 示例项目也演示了它是如何工作的。
排序描述符将如下所示:
// First sort descriptor (required for grouping into sections):
NSSortDescriptor *sortByDate = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
// Second sort descriptor (for the items within each section):
NSSortDescriptor *sortByName = [[NSSortDescriptor alloc] initWithKey:@"firstname" ascending:YES];
[request setSortDescriptors:@[sortByDate, sortByName]];
瞬态“sectionIdentifier”属性的 getter 方法如下所示 (改编自“DateSectionTitles”示例代码):
- (NSString *)sectionIdentifier
[self willAccessValueForKey:@"sectionIdentifier"];
NSString *tmp = [self primitiveValueForKey:@"sectionIdentifier"];
[self didAccessValueForKey:@"sectionIdentifier"];
if (!tmp)
NSDate *date = self.date;
// Using pseudo-code here:
if ("date is from today")
tmp = @"0";
else if ("date is from tomorrow")
tmp = @"1";
else ... // and so on ...
[self setPrimitiveValue:tmp forKey:@"sectionIdentifier"];
return tmp;
要确定日期是否在今天、明天等,您必须使用NSCalendar
方法。
titleForHeaderInSection
方法与此类似(未经测试,如
此答案中的所有其他内容):
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
id <NSFetchedResultsSectionInfo> theSection = [[self.fetchedResultsController sections] objectAtIndex:section];
NSString *sectionName = [theSection name];
if ([sectionName isEqualToString:@"0"])
return @"Today";
else if ([sectionName isEqualToString:@"1"])
return @"Tomorrow";
... // and so on ...
else
return @"Other";
【讨论】:
感谢 Martin R,我已经下载并测试了您告诉我的示例项目,但我看不到如何使用它。非常抱歉,但我不是专业的开发人员,我正在为自己做应用程序,学习如何做事。你建议我在获取请求的日期属性上添加一个第一排序描述符......你能帮我一步一步地完成这个,这不仅对我有帮助,而且对其他试图学习的人都有帮助。 我可以理解您列出的所有步骤,但我不知道实施它们的确切热度。我不想让你为我编写代码,但是你可以举一个例子来做这件事。再次感谢您。 @mvasco:我添加了更多信息,希望对您有所帮助。 再次感谢马丁,我现在将尝试实施您的建议。你帮了我很多。完成后我会告诉你。 Martin,我在以下代码中收到“No visible @interface”错误:[self willAccessValueForKey:@"sectionIdentifier"]; NSString *tmp = [自原始SectionIdentifier]; [self didAccessValueForKey:@"sectionIdentifier"];以上是关于如何使用核心数据实现表格部分的主要内容,如果未能解决你的问题,请参考以下文章