- (void)viewDidLoad {
[super viewDidLoad];
PFObject *Event = [PFObject objectWithClassName:#"Event1"];
Event[#"EventName"] = #"Wine Tasting Event";
Event[#"City"] = #"Newyork";
[Event saveInBackground];
_EventName = Event[#"EventName"];
_City = Event[#"City"];
NSLog(#"%# is happening in %#",_EventName,_City);
}
I have been trying to create parse object 'Event1' to test some data. But when I run the project and refresh core on parse, same rows are created multiple times with differenct objectID. How do I stop this?
Your code explicitly creates and saves a new object every time.
It could be that you manually create the data on the server and add the object id to your code, you can then create the object in the code with no data and the object id (objectWithoutDataWithClassName:objectId:) and use fetch to download the details.
Otherwise you need to run a query to check if the data already exists on the server and create it if not (though you may still get odd duplicates).
Related
I want to send a PFObject directly over a push notification. I send the Parse object directly inside the push (e.g. with a custom key "arg") but I couldn't figure out how to construct a real PFObject from the received data. Received data is (obviously) an NSDictionary, with all the keys (object ID, created at, ACLs etc) available. How do I convert it to a PFObject instance?
I need a real way to construct a PFObject with the available data, so don't come with obvious solutions like "send the object ID and then fetch that object at client with Parse's methods." etc. I already know that obvious solution, but it's time/bandwidth/quota inefficient as it requires a new query, while I can have everything I need in that query anyway.
I'm looking for an automatic way, if any. I am targeting iOS 8 so maximum push payload size is also not an issue (2KB is more than enough for my case).
UPDATE: I've tried [PFObject objectWithClassName:#"MyClassName" dictionary:receivedDictionaryObject]; but no avail. It just does not work, the fields are nil even though the dictionary has all the data directly from Parse itself.
I think you can use something like this
+ (PFObject *)objectFromDictionary:(NSDictionary *)dictionaryFromPush{
PFObject *theObject = [[PFObject alloc] initWithClassName:#"MyClassName"];
for( NSString *keys in [dictionaryFromPush allKeys] )
{
[theObject setObject:[dictionaryFromPush objectForKey:keys] forKey:keys];
}
return theObject;
}
This is an untested code but im pretty sure will give you and idea of my point, to get the NSDcitionary from the Push and sent it to this method to be able to convert it to a PFObject
Hope this help
This question already has an answer here:
Checking for duplicates when importing to CoreData
(1 answer)
Closed 8 years ago.
I have a bunch of NSManagedObjects that are created from a JSON file online. Currently, I am creating them all each time the app launches (not ideal).
What is the best way to check to see if the objects are already there before I try to create them?
if I do [self saveContext] it seems to work, but as I don't know how to check if they are already loaded, it ends up duplicating everything.
Obviously, I am relatively new to Core Data and seem to be missing a key concept.
[EDIT] After reading more and more about where and when to load this many objects into Core Data, it looks like pre-loading the data is the best option for me (the data is static and will likely only be update a few times per year).
I chose not to use the "find or create pattern" as I assumed it would be more expensive given the number of objects that need to be checked/created and would like to save learning about background queues for next time ;)
I was then having trouble getting the sqlite file to work, and solved it by saving the context after each object was created, rather than once after all the objects were loaded.
The way this is handled usually in my experience is via one of the two options:
You first check if the item exists, and if it does, then you update it, else insert it. Here's a sample of what I have used in the past for a vouchers model:
Voucher *newObject = nil;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:#"Voucher"];
request.predicate = [NSPredicate predicateWithFormat:#"voucher_id = %#",[dictionary objectForKey:#"voucher_id"]];
NSError *error = nil;
NSArray *matches = [context executeFetchRequest:request error:&error];
if ([matches count] == 0 ){
newObject = [NSEntityDescription insertNewObjectForEntityForName:#"Voucher" inManagedObjectContext:context];
newObject.number = [json_dictionary objectForKey:#"number"];
newObject.valid_from = [json_dictionary objectForKey:#"valid_from"];
newObject.valid_to = [json_dictionary objectForKey:#"valid_to"];
}
else {
newObject = [matches lastObject];
newObject.number = [json_dictionary objectForKey:#"number"];
newObject.valid_from = [json_dictionary objectForKey:#"valid_from"];
newObject.valid_to = [json_dictionary objectForKey:#"valid_to"];
newObject.voucher_id = [json_dictionary objectForKey:#"voucher_id"];
}
return newObject;
The other way is to select all, put into an NSOrderedSet, and then run a comparison, and only insert if not in the set.
If you look at "Core Data Performance Optimization and Debugging" on this page https://developer.apple.com/wwdc/videos/ , it's got a great explanation of this
If you haven't worked on it before, the learning curve might be a bit steep. But one good way is to use RestKit.
https://github.com/RestKit/RestKit/wiki/Object-mapping#core-data
Ray Wenderlich has a detailed tutorial on Core Data that show you how to do it step by step: (make sure to turn on Google Translate)
In response to your question under comments, here it is:
create a new file and choose to create datamodel (under Core Data)
add your entities - entities are what you declared as class data models. Note that I have Location, Marker, and Village because I have created those as classes (Location.m/.h, etc)]
Add attributes (properties) associated with those entities.
http://i.stack.imgur.com/wOUvF.png
http://i.stack.imgur.com/5AJGZ.png
I'm using Magical Record 2.1 to handle the data persistence in my app. If I create a new entity, set some it's attributes and save, it works fine. However, later, if I fetch that entity, update it's attributes and save, subsequent fetches have the new data until I terminate the app and restart. During the new app session the old data reappears.
This is how I create a new entity:
self.localContext = [NSManagedObjectContext MR_defaultContext];
self.theNewListing = [Listing MR_createInContext:self.localContext];
I'm using MRDefaultContext having read this blog post: http://saulmora.com/2013/09/15/why-contextforcurrentthread-doesn-t-work-in-magicalrecord/
In this case my main attribute is a dictionary, and I set it like this:
NSMutableDictionary *tempDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:#"A description", #"slFieldDescription", etc, etc, nil];
self.theNewListing.dataDictionary = tempDictionary;
This is how I save it:
[self.presentingViewController dismissViewControllerAnimated:YES completion:^(void) {
[self.localContext MR_saveToPersistentStoreWithCompletion:^(BOOL success, NSError *error){
if(!success) {
NSLog(#"%#", error);
}
else {
[self.thePresentingVC refreshCollectionViews:nil];
}
}];
}];
I display my data in a collection view, and at this point everything looks fine. If I terminate and restart the data is still there.
If I fetch the entity again and update the attributes like this:
NSMutableDictionary *newTempDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:#"A new description", #"slFieldDescription", etc, etc, nil];
self.theNewListing.dataDictionary = newTempDictionary;
Then save using the same save code as above, and then update my collection view using the code below, all looks good.
self.listingsArray = [[NSMutableArray alloc] initWithArray:[Listing MR_findAllSortedBy:#"dateListed" ascending:NO]];
[self.mainCollectionView reloadData];
That is, until I quit the app and restart.
If you're wondering, I'm using FTASync, and this only supports MR 2.1, which is why I haven't upgraded to the latest version.
Thanks!
Not sure about MR, nor why you would need it. If that framework can give you the main context, just call the native Core Data save.
[context save:nil];
Cracked it!!
I noticed that my other attributes were saving, just not this one (this one holds all the data that is presented in the UI) and this led me on another line of investigation.
So, it seems that I needed to be working with immutable dictionaries to store this data as explained here:
Core Data saving problem: can't update transformable attribute (NSArray)
I have defined a Core Data for my project and implemented an ENtity:attribute called isRealEntry.
#interface FTRecord : NSManagedObject
#property (nonatomic) NSTimeInterval lastUpdated;
#property (nonatomic) BOOL isRealEntry;
#end
Now when I save the context (NSManagedObjectContext *context;)
NSError *error = nil;
BOOL successful = [context save:&error];
I would like to save only those entities that have a true isRealEntry, otherwise the entry shall be ignored or undone.
How can I achieve this?
Update:
At first I found Martin's solution very promising. However I get a very nasty side effect when I save my data upon entering background:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
[[FTRecordStore sharedStore] saveChanges];
}
When I resume the app, all the previous deleted records aren't gone for real but flagged to be deleted. The array still seems to have all of them (real or unreal in my case). The cells go completely nuts and show empty for all records.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
FTRecord *record = [[[FTRecordStore sharedStore] getAllRecords] objectAtIndex:[indexPath row]];
FTRecordCellView *cell = [tableView dequeueReusableCellWithIdentifier:#"FTRecordCellView"];
[[cell notesLabel] setText:[record notes]];
return cell;
}
I am not sure how to solve this. My Store is a singleton. getAllRecords determines above the content for each cell. Hence I need to have the same value for getAllRecords as also in the tableView, or it would crash.
The other suggested solution with two sources one in memory and in db seems also not to be possible, how do I feed one TableView with two sources?
Update 2:
I had an embarassing oversight. Deleting the record from context is not enough. I also had to delete it from the array.
[allRecords removeObjectIdenticalTo:record];
Therefore I take it back. Martin's solution works perfect. However I am still curious to know if a UITableView can indeed be driven from two sources (db/memory) as suggested in teh other solution. Thanks
I've had to do something similar to this before and the way I approached it was to have a seperate managed object context for items that I was going to persist, and another for items that were staying in memory only.
I went about it by having a seperate persistent store cordinator as well as a separate managed object context that is in memory only, so when items are saved into it, they don't get persisted to the database with what you described as real items.
You can create an in memeory persistent store coordinator like this:
inMemoryPersistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
[inMemoryPersistentStoreCoordinator addPersistentStoreWithType:NSInMemoryStoreType configuration: nil URL: nil options: nil error: &error];
If you want to change non real items into real items, you can copy them into the other managed object context which will persist the items to the database when it's saved.
The obvious issue here is that searching is done on a single managed object context so if you hoped to search through persisted and in memory objects, then you would need to do something more along the lines of what Arkadiusz suggested in his answer.
Saving a managed object contexts saves all changes make to that context. You cannot
exclude some objects from the save operation.
To undo all changes to the "unreal" objects, you could implement the willSave
method of the NSManagedObject subclass:
- (void)willSave
{
if (![self.isRealEntry boolValue]) {
if (self.isInserted) {
// Object was inserted, remove it again:
[self.managedObjectContext deleteObject:self];
} else if (self.isUpdated) {
// Object was modified, undo all changes:
[self.managedObjectContext refreshObject:self mergeChanges:NO];
}
}
}
(I never did this in a real project, but I built a small test app and
it seems to work.)
I don't believe there is a built in way to do this. I believe you would either have to delete them before saving or write cleanup code to find and delete them later.
I am currently updating an app to use Core Data. The app you could say is a "database viewer", only one database is able to be viewed at a time. Each database is kept in its own separate folder. Currently the data is downloaded and stored as a set of plist files.
In the new version I need to convert these plist databases into Core Data stores (one store for each database.) I've already setup the methods that create the separate store files, and crete the entities. The problem is that all the entities are saved to the first database I created, not to the "current" or "lastly created" file.
The basic process I'm using is:
//For each database {
//Create the sqlite file and set up NSManagedObjectContext
[MagicalRecord setupCoreDataStackWithStoreNamed:
[NSURL fileURLWithPath:
[NSString stringWithFormat:#"%#/%#/%#.sqlite",
dirPath, directory, directory]]];
NSManagedObjectContext *managedObjectContext =
[NSManagedObjectContext MR_contextForCurrentThread];
//Iterate through all the plist files and create the necessary entities.
//Save new entities to file
[managedObjectContext MR_save];
//Clean up all cashes
[MagicalRecord cleanUp];
}
How would one properly switch between stores, essentially "reseting" everything between each switch. Preferably (if possible) using magical record.
EDIT:
I've found out a portion of the problem, and removed most of the unwanted behavior. It turns out, you can't reliably call [MagicalRecord cleanUp] on a background thread. Also, It isn't doing what I think it should (see below). I ended up calling back to the main thread after each "save" to reset the Core Data stack. Doing this creates a new context for the first three databases. after that, it duplicates the context from the database three databases ago. So the same three contexts are used in a loop.
This is what I currently have;
I start the process by creating a background thread and run the code to create a single database in the background:
backgroundQueue = dispatch_queue_create("com.BrandonMcQuilkin.myQueue", NULL);
dispatch_async(backgroundQueue, ^(void) {
[self createSQLiteDatabase:updateList];
});
Then creating the stack and database:
- (void)createSQLiteDatabase:(NSArray *)updateList
{
NSString *directory = [updateList objectAtIndex:0];
[MagicalRecord setupCoreDataStackWithStoreNamed:
[NSURL fileURLWithPath:[NSString stringWithFormat:#"%#/%#/%#.sqlite",
dirPath, directory, directory]]];
NSManagedObjectContext *managedObjectContext =
[NSManagedObjectContext MR_contextForCurrentThread];
//Check to see if the stack has reset
NSLog(#"Before:%i", [[Competition MR_findAllInContext:managedObjectContext] count]);
//Create and add entities to context...
//Prepare for next loop
NSLog(#"After:%i", [[Competition MR_findAllInContext:managedObjectContext] count]);
[managedObjectContext MR_saveNestedContexts];
[NSManagedObjectContext MR_resetContextForCurrentThread];
NSMutableArray *temp = [[NSMutableArray alloc] initWithArray:updateList];
[temp removeObjectAtIndex:0];
dispatch_async(dispatch_get_main_queue(), ^(void){
[self shouldContinueUpdating:temp];
});
Then reset everything and repeat for all databases:
- (void)shouldContinueUpdating:(NSArray *)databases
{
//preform cleanup on main thread and release background thread
[MagicalRecord cleanUp];
dispatch_release(backgroundQueue);
if ([databases count] != 0) {
backgroundQueue = dispatch_queue_create("com.BrandonMcQuilkin.myQueue", NULL);
dispatch_async(backgroundQueue, ^(void) {
[self createSQLiteDatabase:databases];
});
}
}
With the two NSLogs, I get this in the console: (using six databases, the pattern is the same no matter how many databases I convert.)
//First Loop
Before:0
After:308
//Second Loop
Before:0
After:257
//Third Loop
Before:0
After:37
//Fourth Loop
Before:308
After:541
//Fifth Loop
Before:257
After:490
//Sixth Loop
Before:37
After:270
... Keep adding to each of the three contexts.
And [MagicalRecord cleanUp] isn't doing what It say it's doing. Here is what the method is supposed to do.
+ (void) cleanUpStack;
{
[NSManagedObjectContext MR_cleanUp];
[NSManagedObjectModel MR_setDefaultManagedObjectModel:nil];
[NSPersistentStoreCoordinator MR_setDefaultStoreCoordinator:nil];
[NSPersistentStore MR_setDefaultPersistentStore:nil];
}
But It turns out that the NSStoreCoordinator every time I save, is the same coordinator, in the same memory location, and each store is hanging around. Something is not working right...
MagicalRecord may not be the best tool for this job for you...
First, let's correct your usage of the setupCoreDataStackWithStoreNamed: method. The parameter takes an NSString, not a URL, nor a file path. MagicalRecord will pick the proper path for you and create your store there. your resulting sqlite file is likely to be named with the path you intended it to be.
Next thing, you'll need to dynamically create your CoreData model for this file. This is kind of tough, but possible. You'll need to traverse these plist files, and interpret entities, attributes and relationships, and create corresponding NSEntityDescriptions, NSAttributeDescriptions and NSRelationshipDesctiptions and populate an NSManagedObjectModel "manually". Youll want to look for the method
- [NSManagedObjectModel setEntities:(NSArray *)]
as well as the creation methods for NSEntityDescription, NSAttributeDescription and NSRelationshipDescription.
You'll also want to save this model somewhere so you don't have to recreate it every time. Luckily, it conforms to NSCoding, so you should just be able to save it to disk.
After that, you'll probably want to populate your data. From here, MagicalRecord can help you. I suggest looking at the Importing Data Made Easy blog post I wrote for Cocoa is My Girlfriend
If you want to "switch stores", which I guess means you want to create a new store for each plist file you've got, then you're going to have to tear down the entire Core Data stack for each file. If you manage to use MagicalRecord for this project, you'll need to look at [MagicalRecord cleanUp], and start over. If each model was the same, you could get by with releasing your Persistent Store Coordinator, and creating a new one to your store. But since your "schemas" will probably be different, you'll just want to scratch everything and start over.
Turns out The problem I'm having is because of a bug in MagicalRecord. I've submitted a git issue here: https://github.com/magicalpanda/MagicalRecord/issues/270