I have the code to actually load the data from my plist into the entity in core data. But where I seem to be stumbling finding any latest posts or info is how to check to see if that entity already contains the data/time to load the data into core data. I can only seem to find outdated non swift fetchrequests to check I don't read anything non swift so I have no idea how to sequence them in swift language....If you need to look at the code I have to actually load the data I can provide it. I know how to read the plist but as far as actually loading the plist to core data is where I am needing the help.
let databaseAlreadyCreated = NSUserDefaults.standardUserDefaults().boolForKey("databaseAlreadyCreated")
if !databaseAlreadyCreated {
//call your function to setup your core data database
NSUserDefaults.standardUserDefaults().setBool(true, forKey:"databaseAlreadyCreated")
NSUserDefaults.standardUserDefaults().synchronize()
}
That's the simplest approach. You can also create another entity for your Core Data which will store applications settings.
Finally, you can try to fetch your entity and if it exists - it means you have already created it. If the results count is 0 - it means that you have to set it up.
Related
I am using core data in my swift project and I am using magical record for core data I want to edit already saved data.
I am fetching editing task like this:
array = Tasks.MR_findByAttribute("task_name", withValue: entryLabel.text)
I am getting data which I want to edit. I am not understanding how to edit this and save in the place of old record. Can anyone please tell me the syntax.
In MagicalRecord, you modify data the same way you would with plain Core Data:
fetch
change attributes / relationships
save
The most commonly used API in MagicalRecord for this is the class method saveWithBlock. In the block you fetch your entities and modify them.
I have to store a collection of custom objects (Dictonary) in Core Data Database.
So far so good. The Dictonary is stored and can be loaded without problems as a "Transformable" object.
The custom Object holds properties, but these are nil after loading them from the Database.
After searching a lot, I haven't found anything for this problem.
It seems that the properties are not getting stored in this way. (Maybe because only the address is stored and not the data??)
Sure it would be better to store an object of Core Data supported datatypes, but in this case the transformable Object is just fine and saves me a lot work and time.
Thank U!
The whole idea of transformable objects is covered in the Core Data Guide. Note that this uses a keyed archiver / unarchiver to create a NSData object from your object or the reverse. This means your customer objects my adhere to NSCoding, and encode all the information in them when asked to as well as handle unencoding.
If your are not doing this now this is the root cause of your problem. What I suggest you do is adopt NSCoding in one custom object, then verify that in fact you can encode it to a NSData object, then from the object unencode it and get the same object back. When you have that working you can then test with Core Data.
I have an application that tracks a user and shows where they've been using MKOverlay. How can I save this information into Core Data so that when the user wants to see where they went yesterday they can load the map/overlay from Core Data?
I have a similar project. Mine is for cycle paths. Here is how I structure my core data model:
I use an order parameter so I can work out how the points connect up. But i think you can just check the 'ordered' property of the relationship now although im not entirely sure how it works. The min / max attributes are for more efficient searches. I store the lat long values as integers to save space after a suggestion to one of my posts. You might find this useful too.
You probably want to add some attributes to the Way such as Date.
You can save any object in a core data model, but if they are not the default type like string, int, etc. you won't be able to query on them.
So you have to construct your entity with property that you will be able to query.
So I see 2 options, you save every information in an entity, but this way you will need to alloc again all objects.
Or you only save the property you will need to query and archive your object in a transformable or in a Binary Data property.
I don't know what would be best.
I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed.
Apple documentation suggests the following :
http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9
However, it seems to rely on the fact that the large objects are applied different mapping.
In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique.
How should I handle a migration with very large objects ?
I'm guessing that you have a bunch of changes you want to make in addition to pulling the data out of blobs. My suggestion is to do the migration in a few stages. I'm kind of thinking out loud here, so it might be possible to improve on this. This requires you to be using SQLite.
To make this work, you're going to have three versions of your model:
The original model
The model with the attribute removed (and possibly with a special unique ID added--see below)
The model with all of the changes you've made, including the addition of the new entity and relationships replacing the attribute
The reason to do this is that the transition from version 1 to 2 should be doable with an automatic lightweight migration. In that case Core Data doesn't need to load anything into memory--it just issues SQL statements to make the changes directly on the database.
So, you start by setting up your persistent store coordinator using the old model version. Once you've loaded the data, go through all of the objects you're migrating, extract the binary attribute, and write it to disk somehow. You can use a fetch request with batching and regular autorelease pool draining to make sure you don't use up too much memory for temporary objects. Store the data into the directory you get with NSCachesDirectory. You'll obviously want to store the data in a way that lets you relate it back to the object's managedObjectID.
Then, you shut everything down and ask Core Data to migrate the store from version 1 to version 2. See this link for details. Open up the store with version 2.
You might have to add a step where you assign some sort of unique ID to each object, because I'm not sure if Core Data maintains object IDs when it does a non-lightweight migration. If you need to do this, your version 2 model would add a new attribute to the object you're taking the binary data out of that would be either optional or have a default value set. Since lightweight migration shouldn't change the managedObjectIDs, you could at save the mapping of your new unique ID to the managedObjectIDs you saved along with the binary data two paragraphs ago.
Save the data and close the store.
Open the store and do a migration from version 2 to version 3, which should basically be the code you already had written before you posted the question. Once the store is open, add all of the objects you saved from the version 1 store and set up the relationships using the data you saved along the way.
Simple, right?
I have an iPhone Core Data app with a pre-populated sqlite "baseline" database. Can I add a second smaller sqlite database with the same tables as my pre-populated "baseline" database but with additional / complementary data such that Core Data will happily union the data from both databases and, ultimately, present to me as if it was all a single data source?
Idea that I had is:
1) the "baseline" database never changes.
2) I can download the smaller "complementary" sqlite database for additional data as and when I need to (I'm assuming downloading sqlite database is allowed, please comment if otherwise).
3) Core Data is then able to union data from 1 & 2. I can then reference this unified data by calling my defined Core Data managed object model.
Hope this makes sense.
Thanks in advance.
Core Data is designed to handle multiple data files via the – addPersistentStoreWithType:configuration:URL:options:error: method. This will allow you to combine all of the data files together and then access them via a single NSManagedObjectContext.
Your only issue, and it may not even be an issue for you, is that the store files cannot directly reference each other. Therefore you will need to reference data between files "manually" via unique identifiers. However I suspect you are already aware of that limitation.
Manual Relationships
The idea is that when both objects in a "relationship" are in one model and one file, Core Data does its magic and handles all of the referential integrity for you. However when they are in different files and/or models this doesn't happen automatically anymore.
The solution to this issue is to use a fetched property that looks up some unique identifier to retrieve the entity (or entities) that you want to be on the other side of the relationship. This will give you a "weak" relationship between files.
One thing to note though when doing this. The fetched property does not get updated automatically when something changes. This means when data changes that would cause that relationship to change, your application will not be automatically made aware of it and you will need to request that property again to get the updated relationship information.
Hopefully that makes it a bit clearer.
Co-existance of fetched properties and relationships
They can definitely co-exist but realize that they are two separate properties. If you want your controller code to see them as one, then I would suggest building a subclass for that entity and then adding a convenience method in there that hits both the relationship and the fetched property and then rolls them up into one NSArray or NSSet before returning it back to your controller code.
You can attach the downloaded database with ATTACH DATABASE statement and operate with unions of tables.