在另一个关于在Core Data支持的UITableView中添加插入行的question中，我提到我的NSFetchedResultsController将它提取的每个对象分配到我的UITableView中的一个单独的部分 . 我认为这只是默认行为，但Marcus S. Zarra说我的控制器配置或我的数据源委托方法可能有问题 . 我承认，我的代码感觉有点像弗兰肯斯坦，其部分内容来自Apple文档和大量教程 . 这是我的第一个程序，也是我第一次使用Core Data，所以请保持温和;）
我的表视图控制器的 Headers 如下：
#import <UIKit/UIKit.h>
#import "RubricAppDelegate.h"
@interface ClassList : UITableViewController {
NSMutableArray *classList;
NSFetchedResultsController *fetchedResultsController;
NSManagedObjectContext *managedObjectContext;
}
@property(nonatomic,retain) NSMutableArray *classList;
@property(nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
@property(nonatomic, retain) NSManagedObjectContext *managedObjectContext;
- (IBAction) grade:(id)sender;
@end
我的实现文件包含一堆虚拟测试数据 . 我包括，以防我使用不正确的方法来实例化核心数据对象 . 基本上，我想知道我的NSFetchedResultsController是否应该将我的对象（在本例中是myClass的实例）返回到单独的部分 . 如果是这样，我在做什么来创造这个问题？
目前的最终目标是让我能够在我的桌面顶部添加一个插入单元格（我知道将它放在底部是"standard,"但我喜欢它在应用程序中看起来如何反过来） . 您会注意到我的 -tableView:editingStyleForRowAtIndexPath: 将第0部分的单元格样式设置为insert，但当然我需要弄清楚如何在单元格1而不是单元格0开始myClass.classTitle的列表（这就是为什么我要确定是否有每个分配给自己的部分的对象是正常的） .
这是我的实现文件：
#import "ClassList.h"
#import "ClassRoster.h"
#import "RubricAppDelegate.h"
#import "Student.h"
#import "myClass.h"
@implementation ClassList
@synthesize classList;
@synthesize fetchedResultsController;
@synthesize managedObjectContext;
#pragma mark -
#pragma mark View lifecycle
- (void)viewDidLoad {
[super viewDidLoad];
self.editing = YES;
RubricAppDelegate *appDelegate = (RubricAppDelegate *)[[UIApplication sharedApplication] delegate];
managedObjectContext = [appDelegate managedObjectContext];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"myClass" inManagedObjectContext:managedObjectContext];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entity];
//test data
myClass *newClass = (myClass *) [NSEntityDescription insertNewObjectForEntityForName:@"myClass" inManagedObjectContext:managedObjectContext];
newClass.classTitle = @"UFDN 1000";
NSNumber *ID = [NSNumber numberWithInt:1];
newClass.classID = ID;
Student *newStudent = (Student *) [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:managedObjectContext];
newStudent.classID = ID;
newStudent.studentName = @"Andy Albert";
newStudent.studentUsername = @"albera";
[newClass addStudentsObject:newStudent];
newStudent.classID = ID;
newStudent.studentName = @"Bob Dole";
newStudent.studentUsername = @"doleb";
[newClass addStudentsObject:newStudent];
newStudent.classID = ID;
newStudent.studentName = @"Chris Hanson";
newStudent.studentUsername = @"hansoc";
[newClass addStudentsObject:newStudent];
myClass *newClass2 = (myClass *) [NSEntityDescription insertNewObjectForEntityForName:@"myClass" inManagedObjectContext:managedObjectContext];
newClass2.classTitle = @"UFDN 3100";
ID = [NSNumber numberWithInt:2];
newClass2.classID = ID;
newStudent.classID = ID;
newStudent.studentName = @"Danny Boy";
newStudent.studentUsername = @"boyd";
[newClass2 addStudentsObject:newStudent];
newStudent.classID = ID;
newStudent.studentName = @"James Matthews";
newStudent.studentUsername = @"matthj";
[newClass2 addStudentsObject:newStudent];
newStudent.classID = ID;
newStudent.studentName = @"Aaron Todds";
newStudent.studentUsername = @"toddsa";
[newClass2 addStudentsObject:newStudent];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"classID" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
NSError *error;
fetchedResultsController = [[NSFetchedResultsController alloc]
initWithFetchRequest:request
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:@"classTitle" cacheName:nil];
[fetchedResultsController performFetch:&error];
UIBarButtonItem *gradeButton = [[UIBarButtonItem alloc]
initWithTitle:@"Grade"
style:UIBarButtonItemStylePlain
target:self
action:@selector(grade:)];
self.navigationItem.rightBarButtonItem = gradeButton;
[gradeButton release];
}
- (IBAction) grade:(id)sender {
}
#pragma mark -
#pragma mark Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
NSLog(@"Number of sections = %d", [[fetchedResultsController sections] count]);
return ([[fetchedResultsController sections] count]);
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
id <NSFetchedResultsSectionInfo> myClass = [[fetchedResultsController sections] objectAtIndex:section];
NSLog(@"Number of classes = %d", [myClass numberOfObjects]);
return [myClass numberOfObjects];
}
// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
myClass *theClass = [fetchedResultsController objectAtIndexPath:indexPath];
NSLog(@"Class name is: %@", theClass.classTitle);
cell.textLabel.text = theClass.classTitle;
}
return cell;
}
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section == 0) {
return UITableViewCellEditingStyleInsert;
}
else return UITableViewCellEditingStyleDelete;
}
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
if (editingStyle == UITableViewCellEditingStyleDelete) {
myClass *result = (myClass *)[fetchedResultsController objectAtIndexPath:indexPath];
[managedObjectContext deleteObject:result];
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];
}
else if (editingStyle == UITableViewCellEditingStyleInsert) {
}
}
#pragma mark -
#pragma mark Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// Navigation logic may go here. Create and push another view controller.
/*
<#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
// ...
// Pass the selected object to the new view controller.
[self.navigationController pushViewController:detailViewController animated:YES];
[detailViewController release];
*/
}
#pragma mark -
#pragma mark Memory management
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Relinquish ownership any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
// Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
// For example: self.myOutlet = nil;
}
- (void)dealloc {
[classList release];
[super dealloc];
}
@end
我的RubricAppDelegate基本上与Apple文档相同，用于设置Core Data NSManagedObjectContext，NSPersistentStoreCoordinator等 . 但是，如果您认为可能存在问题，请告诉我，我会发布它 .
编辑：我忘了提到两个原因，我知道每个对象被分配到不同的部分 .
1） NSLog(@"Number of sections = %d", [[fetchedResultsController sections] count]); -numberOfSectionsInTableView: 内部返回我拥有的myClass对象的数量 .
2）如果我设置 -numberOfSectionsInTableView: 返回1，我的表只显示一个对象并切断其余的对象 .
1 回答
您有段，因为您通过在初始化FRC时传递
sectionNameKeyPath:的非Nil值来告诉获取的结果控制器创建它们 .更改：
...至：
......这些部分将会消失 . 否则，FRC将为商店中
classTitle属性的每个值创建一个部分 . 如果每个myClass实例具有不同的classTitle值，则每个实例在tableview中都有自己的部分 .