更新：
我对这个方法有这个问题： 默认情况下，视图会将当天设置为今天，并创建会话，将今天的日期作为timeStamp，除非用户手动更改日期。
如果我在今天的日期添加运动，一切都很好。
如果我选择上一个日期并为其添加练习，看起来很好，但似乎练习不仅会添加到此前一个日期，还会添加到今天。
因此，无论我选择的是什么日期，都会将该实体实体添加到该会话和今天的会话中。
因此，当我在tableview中查看今天的会话时，它会完成所有练习，因为所有内容都会随着手动选择的日期一起添加到今天。
我该如何解决这个问题？
原始：
我有一个detailViewController，它负责处理核心数据对象Session，Exercise，＆amp;设置。
视图的目的是让用户输入有关健身锻炼的详细信息。默认情况下，日期设置为今天，但用户可以将其更改为以前的日期。在createSession中，当用户按下该日期的完成按钮并且日期尚不存在时，将创建一个具有该日期时间戳的新Session对象。如果它已经存在，则使用该timeStamp日期获取该对象。
问题是，即使用户以后没有输入必要的数据，也会创建一个新的Session对象。创建会话后，将提示用户输入用于练习的权重和代表。如果用户没有输入此信息（对象集），则会有一个没有用途的Session对象，因为它们没有练习并且设置了与之相关的对象。
但是我在检查weight / rep之前创建Session对象的原因是因为如果获取了Session，我想在视图中显示它的属性数据，因此我需要在添加sets / reps之前使用它。 / p>
我目前的代码是：
-(void)createSession
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat: @"(timeStamp >= %@ && timeStamp <= %@)", targetDateBegins, targetDateEnds]];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"Session" inManagedObjectContext:managedObjectContext]];
NSError *error = nil;
NSArray *results = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
NSLog(@"Fetch error: %@", error);
if ([results count])
{
session = (Session *)[results objectAtIndex:0];
}
else
{
session = (Session *)[NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:managedObjectContext];
session.timeStamp = self.picker.date;
}
NSSet *filteredExercisesFromSession=[session.exercises filteredSetUsingPredicate:[NSPredicate predicateWithFormat: @"name == %@",selectedExerciseName]];
if ([filteredExercisesFromSession count] > 0)
{
self.exercise=[filteredExercisesFromSession anyObject];
}
else
{
self.exercise = (Exercise *)[NSEntityDescription insertNewObjectForEntityForName:@"Exercise" inManagedObjectContext:managedObjectContext];
self.exercise.name = selectedExerciseName;
[session addExercisesObject:exercise];
}
if (![managedObjectContext save:&error])
{
// Handle the error.
}
NSLog(@"Save error: %@", error);
[fetchRequest release];
self.fetchedResultsController = nil;
[setsTableView reloadData];
}
-(IBAction)createSet
{
Set *set = (Set *)[NSEntityDescription insertNewObjectForEntityForName:@"Set" inManagedObjectContext:managedObjectContext];
set.weight = [NSNumber numberWithFloat:weightSelected2];
set.reps = [NSNumber numberWithInt:repSelected];
set.timeStamp = self.picker.date;
[self.exercise addSetsObject:set];
NSError *error = nil;
if (![managedObjectContext save:&error])
{
// Handle the error.
}
NSLog(@"error: %@", error);
self.fetchedResultsController = nil;
[setsTableView reloadData];
}
我正在尝试保持新代码与此不太相似，也许我可以调整一些事情而不是创建一些全新的代码。
编辑：
这是我到目前为止的一点点，有点卡住但仍在努力。感谢
//Session.h
@interface Session : NSManagedObject {
NSString * const kSessionLeavingActiveSession = @"kSessionLeavingActiveSession";
NSString * const kSessionChangingActiveSession = @"kSessionChangingActiveSession";
static Session *activeSession = nil;
//Session.h
@implementation Session
// a static method to retrieve & create if nil the active session
+ (Session *)activeSession {
if (activeSession = nil)
{
session = (Session *)[NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:managedObjectContext];
}
}
+ (Session *)sessionForDate:(NSDate *)date andSetActive:(BOOL)isActive {
NSCalendar *calendar = [NSCalendar currentCalendar];
unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *dateComponentsForToday = [calendar components:unitFlags fromDate:self.picker.date];
[dateComponentsForToday setHour:0];
[dateComponentsForToday setMinute:0];
[dateComponentsForToday setSecond:0];
NSDate *targetDateBegins = [calendar dateFromComponents:dateComponentsForToday];
NSDate *targetDateEnds = [targetDateBegins dateByAddingTimeInterval:(60 * 60 * 24 - 1)];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat: @"(timeStamp >= %@ && timeStamp <= %@)", targetDateBegins, targetDateEnds]];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"Session" inManagedObjectContext:managedObjectContext]];
NSError *error = nil;
NSArray *results = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
NSLog(@"Fetch error: %@", error);
if ([results count])
{
session = (Session *)[results objectAtIndex:0];
NSLog(@"Already have session for date: %@", session.timeStamp);
}
else
{
session = (Session *)[NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:managedObjectContext];
session.timeStamp = self.picker.date;
NSLog(@"New session for date: %@", session.timeStamp);
}
//send Notification kSessionChangingActiveSession if isActive == YES
//if isActive is true, set it to the active session.
}
+ (void)saveOrDestroyActiveSession {
//register this function as an observer on kSessionChangingActiveSession
//before the active session is changed, you will be able to determine
//if the session has anything associated with it, and persist it, or
//destroy it.
//determine if it has exercises assigned to it.
//if it does, save the context.
//if it doesn't destroy the active session and set activeSession to nil
}
+ (void)saveActiveSession {
//register this function as an observer on kSessionLeavingActiveSession.
//If you are leaving an area of the application where you are working on
//the session, you want to send this notification so that you can save
//the session if you have added exercises.
//you don't want to delete it though, if you can still go back to the
//active session, for example, if it's the active session view controller
//on a tab controller.
}
// the rest of your session methods
@end
//your app delegate
- (void)applicationWillResignActive:(UIApplication *)application {
//send a notification that you are leaving the active session
}
//viewController.m
//modify your fetched results controller to pull it's list of exercises from the
//active session, in case it's not saved you can still retrieve the exercises associated
//with it.
- (void)viewDidUnload {
//send a notification that you are leaving the active session
}
- (void)createSession {
Session *activeSession = [Session sessionForDate:self.picker.date andSetActive:YES];
NSSet *filteredExercisesFromSession=[session.exercises filteredSetUsingPredicate:[NSPredicate predicateWithFormat: @"name == %@",selectedExerciseName]];
if ([filteredExercisesFromSession count] > 0)
{
self.exercise=[filteredExercisesFromSession anyObject];
}
else
{
self.exercise = (Exercise *)[NSEntityDescription insertNewObjectForEntityForName:@"Exercise" inManagedObjectContext:managedObjectContext];
self.exercise.name = selectedExerciseName;
[session addExercisesObject:exercise];
}
//if you've added exercises go ahead and save.
//if you haven't let the observers take care of persisting or destroying it.
}
答案 0 :(得分：1)
这可能比我想写的要脏一些，但它应该让你对我如何解决问题的看法有所了解。
//Session.m
//Check out the link to PSFoundation and the ActiveRecord Core Data methods
//https://github.com/steipete/PSFoundation/tree/master/activerecord-coredata
NSString * const kSessionLeavingActiveSession = @"kSessionLeavingActiveSession";
NSString * const kSessionChangingActiveSession = @"kSessionChangingActiveSession";
static Session *activeSession = nil;
@implementation Session
// ....
// a static method to retrieve & create if nil the active session
+ (Session *)activeSession {
//if activeSession = nil create a new instance
//reading the code it looks like you only create a new session if there
//isn't a session that already exists for the day chosen in the date picker?
//If that's the case, then it is only possible for there ever to be
//a single instance of an active session, one which is currently in view.
}
+ (Session *)sessionForDate:(NSDate *)date andSetActive:(BOOL)isActive {
//wrap all of your create session logic in here.
//search for a session that exists for this date, and return it if
//it exists, or create a new session if it doesn't.
//send Notification kSessionChangingActiveSession if isActive == YES
//if isActive is true, set it to the active session.
}
+ (void)saveOrDestroyActiveSession {
//register this function as an observer on kSessionChangingActiveSession
//before the active session is changed, you will be able to determine
//if the session has anything associated with it, and persist it, or
//destroy it.
//determine if it has exercises assigned to it.
//if it does, save the context.
//if it doesn't destroy the active session and set activeSession to nil
}
+ (void)saveActiveSession {
//register this function as an observer on kSessionLeavingActiveSession.
//If you are leaving an area of the application where you are working on
//the session, you want to send this notification so that you can save
//the session if you have added exercises.
//you don't want to delete it though, if you can still go back to the
//active session, for example, if it's the active session view controller
//on a tab controller.
}
// the rest of your session methods
@end
//your app delegate
- (void)applicationWillResignActive:(UIApplication *)application {
//send a notification that you are leaving the active session
}
//viewController.m
//modify your fetched results controller to pull it's list of exercises from the
//active session, in case it's not saved you can still retrieve the exercises associated
//with it.
- (void)viewDidUnload {
//send a notification that you are leaving the active session
}
- (void)createSession {
Session *activeSession = [Session sessionForDate:self.picker.date andSetActive:YES];
//code to add exercises to session
//if you've added exercises go ahead and save.
//if you haven't let the observers take care of persisting or destroying it.
}