EDIT:
I have altered the NSPredicate as recommended so that my fetch code look like so. Having printed to the UITextView like this, when I press load it spits out the following:
<NSManagedObject: 0x1c7cf0>(entity: DatedText; id: 0x1420c0 <x - coredata://B52D4F88-0210-4AE2-9DA6-C05ED64FE389/DatedText/p12> ; data: <fault>)
So either its not getting any data data because it hasn't been saved/loaded correctly or I am trying to get the loaded result into a UITextView the incorrect way. Any ideas?
NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
NSEntityDescription *testEntity = [NSEntityDescription entityForName:#"DatedText" inManagedObjectContext:self.managedObjectContext];
[fetch setEntity:testEntity];
NSPredicate *pred = [NSPredicate predicateWithFormat:#"dateSaved == %#", datePicker.date];
[fetch setPredicate:pred];
NSError *fetchError = nil;
NSArray *fetchedObjs = [self.managedObjectContext executeFetchRequest:fetch error:&fetchError];
if (fetchError != nil) {
NSLog(#" fetchError=%#,details=%#",fetchError,fetchError.userInfo);
return nil;
}
NSString *object = [NSString stringWithFormat:#"%#",[fetchedObjs objectAtIndex:0]];
noteTextView.text = object;
I have been having all sorts of problems working out how to use Core Data, so I have gone back to basics, new window based ipad project using core data.
I have added a view and some code which doesn't work, hehe. Im basically trying to save some text to a date, then when going back to that date, the text which was previously saved will be shown again.
There's a tutorial on iPhone developer site here. And there are several sample codes with Core Data as well. These should get you started.
I checked your project and aside from having to synthesize the CoreData properties, I also just noticed you were trying to assign an NSArray to your fetch predicate, but it actually expects an NSPredicate object. You should use this instead:
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(dateSaved == %#)", datePicker.date];
[fetch setPredicate:pred];
If you want to set more than 1 predicate you should do that on your predicate string i.e.
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(dateSaved == %#) AND (dateSaved <= %#", datePicker.date, [NSDate date]];
Cheers,
Rog
You most likely crashing because your ivar is managedObjectContext_ but you are using self.managedObjectContext. You also need to synthesize the core data ivars even if you provide a custom getter.
You're setting your NSFetchRequest's predicate to an NSArray, not an NSPredicate.
If you had posted the actual crash, it would probably say something like an unknown selector was sent to an instance of NSArray.
Related
i have a list of objects being managed by CoreData. i want to get a specific object out of CoreData using an NSPredicate. below is the code i am using. Array arr always comes back with 0 objects in it presumably because the fetch cant find an object that matches the predicate. i know for a fact that at least 1 object in CoreData has an advertisement.uuid that matches adUdid. i have manually gotten the entire list of objects and searched it myself for the uuid and found it. advertisement is a member of WebServiceAuthService_mobileAdvertisementVO and uuid is a member of advertisement. whats even more aggregating is the fact that this exact code works just fine in another project. im at a loss to figure out why this code no longer works in the new project.
incase it matters this code is in a static library i am making.
EDIT: arr is always empty so there is nothing to post. there are also no errors being given. its just not working. the uuids are NSStrings something along the lines of "9ca98efe-ef48-47c0-aff5-058224b3093d". i have a feeling the problem may be elsewhere in the code and just manifesting itself here.
WebServiceAuthService_mobileAdvertisementVO *mobileAd = nil;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"WebServiceAuthService_mobileAdvertisementVO" inManagedObjectContext:managedObjectContext];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"advertisement.uuid == %#",adUdid];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];
NSError *error = nil;
NSArray *arr = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
[fetchRequest release];
if (error)
{
DLog(#"fetched special ad error: %#",[error localizedDescription]);
}
if (arr && [arr count] >= 1)
{
DLog(#"found ad with UUID %#",adUdid);
for (WebServiceAuthService_mobileAdvertisementVO *obj in arr)
{
NSManagedObjectID *objID = [obj objectID];
if (![objID isTemporaryID])
{
mobileAd = obj;
}
}
}
You are comparing strings, in which case LIKE is a better operator than ==. So:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"advertisement.uuid LIKE %#",adUdid];
Don't worry about quotes, predicateWithFormat: will automatically put single quotes around the right hand term.
EDIT:
Reference: Predicate Programming Guide
This question already has answers here:
Querying Core Data with Predicates - iPhone
(4 answers)
Closed 2 years ago.
I have an app that has multiple tableviews and I want to use Core Data to capture all the data. I have two entities - freezers and items. In the first tableview I add a freezer and it saves correctly. I quit the app, re-open, and it is there. I click on the freezer (opening another tableview) and add some items and I can see them in my new sectioned tableview. I quit my app, restart it, see the freezer, click on it and there are no items.
I have my managedObjectContext in my appDelegate and reference it from there using all views, so I am not creating multiple instances. Here is the code I use to save the items to a freezer, both the managedObjectContext and my itemsArray:
Item *item = (Item *)[NSEntityDescription insertNewObjectForEntityForName:#"Item" inManagedObjectContext:[delegate managedObjectContext]];
[item setFreezer:freezerName];
[item setName:name];
[item setQuantity:quantity];
[item setSection:section];
[item setAdded:added];
[item setNotes:notes];
NSError *error = nil;
if (![[delegate managedObjectContext] save:&error]) {
NSLog(#"Freezer info didn't save. Need to handle this.");
}
[items insertObject:item atIndex:0];
Here is the code I use in the ItemViewController to retrieve the items within viewDidLoad:
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"freezer == '%#'", freezerName];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Item" inManagedObjectContext:[delegate managedObjectContext]];
NSSortDescriptor *sorts = [[NSSortDescriptor alloc] initWithKey:#"section" ascending:NO];
NSArray *sort = [[NSArray alloc] initWithObjects:sorts, nil];
[request setSortDescriptors:sort];
[request setEntity:entity];
[request setPredicate:predicate];
NSError *error = nil;
NSMutableArray *results = [[[delegate managedObjectContext] executeFetchRequest:request error:&error] mutableCopy];
if(results == nil) {
NSLog(#"Error fetching results... need to handle");
}
[self setItems:results];
NSLog(#"items count:%d", [items count]);
The item count returned is zero.
I am completely stumped and have spent several hours searching online, trying different things, and I can't figure it out. I know there are some much smarter coders out there and I hope one of you can see what the problem is.
I would try to change the predicate to
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"freezer like %#", freezerName];
Hope that helps!
Maybe the problem is that you load data in
- viewDidLoad:
method. It's called only once when your view is loaded, so when underlaying data get's changed, your view controller is not aware about it.
You can either move your loading code to
- viewWillAppear:
method or introduce notifications to spread the information that data store has changed its state and reload table views upon that event.
The best way is probably to use NSFetchedResultsController as your data source, as its always aware of its data store changes. Check docs for reference to that class.
I'm trying to fetch objects from core data that are not in a given set, but I haven't been able to get it to work.
For instance, suppose that we have a core data entity named User, which has a few attributes such as userName, familyName, givenName, and active. Given an array of strings representing a set of usernames, we can easily fetch all the users corresponding to that list of usernames:
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] init];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"User"
inManagedObjectContext:moc];
[request setEntity:entity];
NSArray *userNames = [NSArray arrayWithObjects:#"user1", #"user2", #"user3", nil];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"userName IN %#", userNames];
[request setPredicate:predicate];
NSArray *users = [moc executeFetchRequest:request error:nil];
However, I want to fetch the complement of that set, i.e., I want all the users in core data that don't have the usernames specified in the userNames array. Does anyone have an idea how to approach this issue? I thought it would be simple enough to add a "NOT" in the predicate (i.e., "userName NOT IN %#"), but Xcode throws an exception saying the predicate format could not be parsed. I also tried using the predicate builder available for fetch requests with no luck. The documentation wasn't particularly helpful either. Suggestions? Comments? Thanks for all your help :)
In order to find the objects that aren't in your array, all you have to do is something like this:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"NOT (userName IN %#)", userNames];
That should return a request of all the objects without the ones you specified
I am not strong at core data/objective-c but the predicate should be like the following statement;
[predicateFormat appendFormat:#"not (some_field_name in {'A','B','B','C'})"];
An example:
NSMutableString * mutableStr = [[NSMutableString alloc] init];
//prepare filter statement
for (SomeEntity * e in self.someArray) {
[mutableStr appendFormat:#"'%#',", e.key];
}
//excluded objects exist
if (![mutableStr isEqual:#""])
{
//remove last comma from mutable string
mutableStr = [[mutableStr substringToIndex:mutableStr.length-1] copy];
[predicateFormat appendFormat:#"not (key in {%#})", mutableStr];
}
//...
//use this predicate in NSFetchRequest
//fetchRequest.predicate = [NSPredicate predicateWithFormat:predicateFormat];
//...
Here's another useful example, showing how to take a list of strings, and filter out any which DON'T start with the letters A-Z:
NSArray* listOfCompanies = [NSArray arrayWithObjects:#"123 Hello", #"-30'c in Norway", #"ABC Ltd", #"British Rail", #"Daily Mail" #"Zylophones Inc.", nil];
NSPredicate *bPredicate = [NSPredicate predicateWithFormat:#"NOT (SELF MATCHES[c] '^[A-Za-z].*')"];
NSArray *filteredList = [listOfCompanies filteredArrayUsingPredicate:bPredicate];
for (NSString* oneCompany in filteredList)
NSLog(#"%#", oneCompany);
I use this kind of NSPredicate when I'm populating a UITableView with an A-Z index, and want an "everything else" section for items which don't start with a letter.
I have the following Core Data setup:
Project has-many Answer
Field has-many Answer
Answer has-one Field
Answer has-one Project
I need to find the Answer for each Field that is also owned by Project. I'm currently using a predicate for this and executing a fetch request:
NSEntityDescription *answerEntity = [NSEntityDescription entityForName:#"Answer" inManagedObjectContext:self.managedObjectContext];
NSPredicate *answerPredicate = [NSPredicate predicateWithFormat:#"ANY project == %# && field == %#", self.project, self.field];
NSFetchRequest *answerRequest = [[NSFetchRequest alloc] init];
[answerRequest setEntity:answerEntity];
[answerRequest setPredicate:answerPredicate];
NSError *error = nil;
NSArray *predicates = [self.managedObjectContext executeFetchRequest:answerRequest error:&error];
I'm still new to Core Data but I believe the fetchRequest is querying the database each time I call it, is there a more efficient way of finding these Answer objects?
If I understand correctly, you already have a Field object and an Project object and you want to find the Answer objects they have in common.
If so, the solution is a simple intersect set operation:
NSSet *answersInCommon=[[aFieldObj mutableSetValueForKey:#"answers"] intersectSet:[aProjectObj mutableSetValueForKey:#"answers"]];
... which will return only those Answer objects that appear in both relationships.
Update:
#pdenya in comment provides an enhancement :
Just want to clarify a minor error and a small point that makes this less than ideal. intersectSet returns (void) so the syntax for this would be:
NSMutableSet *answers=[field mutableSetValueForKey:#"answers"];
[answers intersectSet:[project mutableSetValueForKey:#"answers"]];
This solution also modifies the aFieldObj.answers array meaning you can't use this while iterating. setWithSet clears this right up. Example:
NSMutableSet *answers = [NSMutableSet setWithSet:[project mutableSetValueForKey:#"answers"]];
[answers intersectSet:[field mutableSetValueForKey:#"answers"]];
#pdenya's is the correct form.
Best alternate method I've found so far:
NSMutableSet *answers = [self.project mutableSetValueForKey:#"answers"];
NSPredicate *answerPredicate = [NSPredicate predicateWithFormat:#"field == %#", field];
[answers filterUsingPredicate:answerPredicate];
NSManagedObject *answer = nil;
if([answers count] > 0) {
answer = [[answers allObjects] objectAtIndex:0];
}
I'm trying to retrieve data from Core Data and put it into a Mutable Array
I have an Entity called 'Stock' and in Properties, attributes called : code, price & description...
How do I get the data stored in these attributes into a simple Mutable Array?
I've added this code...
NSMutableArray *array = [[NSMutableArray alloc]init];
[array addObject:[stock valueForKey:#"code"]];
and I get this error...
'-[NSCFArray insertObject:atIndex:]: attempt to insert nil'
I have a 'Managed Object Class' called 'Stock' and declared called stock. Am I missing something?
If I do this in the -cellForRowAtIndexPath...
Stock *stock1 = [fetchedResultsController objectAtIndexPath:indexPath];
array = [[NSMutableArray alloc] init];
[array addObject:stock1.code];
NSLog(#"Filtered List is? %#", array);
In the console I can see these 2 items
'The Filtered array is 810005'
'The Filtered array is 810007
'
What must I do to get these items(810005 & 810007) into an array set up in the -viewDidLoad method? Like it does in the -cellForRowAtIndexPath?
Update
Hi Marcus,
Finally got it working (well, 80%)
I put this in the -cellForRowAtIndexPath
Stock *product = nil;
if (tableView == self.searchDisplayController.searchResultsTableView)
{
filteredListContent = [NSMutableArray arrayWithObjects:stock1.code, nil];
product = [self.filteredListContent objectAtIndex:indexPath.row];
[self configureFilteredCell:cell atIndexPath:indexPath];
[filteredListContent objectAtIndex:indexPath.row];
NSLog(#"Filtered List Array List is? %#", stock1.code);
}
else
{
listContent = [NSMutableArray arrayWithObjects:stock1.code, nil];
[self configureCell:cell atIndexPath:indexPath];
NSLog(#"List Array List is? %#", stock1.code);
}
Then I used this code in the scope
- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
self.savedSearchTerm = searchText;
if (searchText !=nil)
{
NSPredicate *predicate =[NSPredicate predicateWithFormat:#"code beginsWith[cd] %#", searchText];
[fetchedResultsController.fetchRequest setPredicate:predicate];
}
else
{
NSPredicate *predicate =[NSPredicate predicateWithFormat:#"code contains[cd] %#", searchText];
[fetchedResultsController.fetchRequest setPredicate:predicate];
[self.tableView reloadData];
}
NSError *error = nil;
if (![[self fetchedResultsController] performFetch:&error])
{
// Handle error
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
[self.tableView reloadData];
Everything is filtering fine but when I hit cancel on the search, it's not reloading the original data...
I won't be defeated...!!
Thanx
Since you are having this issue in your -viewDidLoad, I am guessing (and without the code from -viewDidLoad, it is only a guess) that you are trying to fetch objects from the NSFetchedResultsController before the -executeFetch: has been called on the controller and therefore you are in the land of nils.
I would suggest setting a break point in your -viewDidLoad and watching the values and you walk through your code. This will tell you what is nil and where.
Of course a better question is, why are you trying to put NSManagedObject instances into a NSMutableArray? Since they are already in your NSFetchedResultsController is there really a need to build up another array? What is the end goal?
Update
Now I understand what you are trying to do.
Solution 1
Only populate the array when a search has been conducted. Take a look at the http://developer.apple.com/iphone/library/samplecode/TableSearch/index.html example code and you should see how to apply it to your situation.
If you want to enter the table view with a pre-defined search then you need to perform it after you have executed a -performFetch: in the NSFetchedResultsController.
Solution 2
Modify the NSPredicate on the NSFetchedResultsController to include your search terms and then execute -performFetch: on the NSFetchedResultsController, you may have to do a -reloadData on the table as well, I am not sure.
When the user clears the search field you reset the predicate and re-fetch everything. Since it is all cached there should be no performance penalty.
Solution 2 just occurred to me and I have not tested it personally but there is no reason it shouldn't work just fine. Should even give you live updates within the search.
Have you read the documentation? You fetch your Stock instances (all of them or filter them with a predicate), then do with them whatever you please.
You can then add their properties to an array individually:
[array addObject:[stockInstance valueForKey:#"price"];
... or use a combination of < NSKeyValueCoding > protocol methods such as -dictionaryWithValuesForKeys: NSDictionary methods such as -objectsForKeys:notFoundMarker: to get an array for given keys.
This may or may not actually be what you need to do, though. It depends on what you intend to use the resulting array for. If you want a quick sum of all matching Stock instances' "price" values, for example, you can use Set and Array Operators. It really depends on what you're trying to achieve.
When I got your error,
'-[NSCFArray insertObject:atIndex:]: attempt to insert nil'
I had given the fetchedRequest a sort descriptor that had a nil key. The error appeared when I used these lines:
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:nil ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
The error disappeared when I set the key to #"name":
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];