I am watching/doing the iTunes U Stanford iPhone course. (provided for free!). I am on the paparazzi program trying to figure out Core Data.
Below is how I save data into coreData, how do I verify this information actually got saved?
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
FlickrFetcher *ff = [FlickrFetcher sharedInstance];
if (![ff databaseExists])
{
NSString *path = [[NSBundle mainBundle] pathForResource:#"FakeData" ofType:#"plist"];
NSArray *data = [NSArray arrayWithContentsOfFile: path];
NSManagedObjectContext *managedObjectContext = [ff managedObjectContext];
NSError *error = nil;
for (NSDictionary *row in data)
{
Person *person = (Person *)[NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:managedObjectContext];
Photo *photo = (Photo *)[NSEntityDescription insertNewObjectForEntityForName:#"Photo" inManagedObjectContext:managedObjectContext];
photo.name = [row objectForKey:#"name"];
photo.url = [row objectForKey:#"path"];
person.name = [row objectForKey:#"user"];
[person addPhotosObject:photo];
}
[managedObjectContext save:&error];
}
In your code you would check whether error is nil after you have sent the save: message to the managedObjectContext, or alternatively, whether the return value of that expression is YES. If that's the case, it means there were no errors while saving your changes in the context.
If you just want to check by hand (e.g. after already running the code previously), you can of course simply open the SQLite database in some browser and check the data is there. SQLite Manager extension for Firefox is a nice tool for that.
Related
I'm trying to save a string into a database every time a button is pressed but when I run the project, I get that on my console: 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Info''.
Referring to the Data Model, I have created a .xcdatamodeld with an Entity named 'Info' and, inside it, an attribute named 'path' with a type of string.
I've created three functions. "enterdata" Checks if the name is avaliable or not by calling "findData". If the name is avaliable, a new data is recorded throught "newData", if not, it looks for a different name.
I've been looking for some similar questions and I've found out this. It says that de ManagedObjectContext has to be passed to the View Controller but I don't understand what does it mean.
Here's my .h code:
#property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
Here's my .m code:
#import <CoreData/CoreData.h>
#synthesize managedObjectContext;
int iSavedNum = 1;
bool bCanSave;
//Enter data
- (IBAction) enterdata:(id)sender {
//Search if data is already registered
NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *path = [NSString stringWithFormat:#"%#/info%i.png",docDir, iSavedNum];
[self findData:path :#"path"];
//If data is already saved, save it with new name.
if (bCanSave == NO) {
for (iSavedNum = 1; bCanSave == YES; iSavedNum++) {
[self findData:path :#"path"];
if (bCanSave == YES) {
[self newData:path :#"path"];
}
}
} else {
[self newData:path :#"path"];
}
}
//Input new data
- (void) newData:(NSString *)value:(NSString *)key {
//Create ManagedObjectContext and ManagedObjectModel
__0AppDelegate *appDelegate = (__0AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSManagedObjectModel *newRecord;
//Put the data to the Entity
NSString *entityName = #"Info";
newRecord = [NSEntityDescription insertNewObjectForEntityForName:entityName inManagedObjectContext:context];
[newRecord setValue:value forKey:key];
//Errors management and cheking
NSError *error;
[context save:&error];
NSLog(#"Info Saved. Value: %# Key: %#", value, key);
}
//Find Data
- (void) findData:(NSString *)valor:(NSString *)key {
//Create ManagedObjectContext
__0AppDelegate *appDelegate = (__0AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
//Call the Entity and make a request
NSString *entityName = #"Info";
NSEntityDescription *entityDesc = [NSEntityDescription entityForName:entityName inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDesc];
//Create predicate to call specific info
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(%# = %#)", key, valor];
[request setPredicate:pred];
//Errors management and creation of an array with found info
NSError *error;
NSArray *objects = [context executeFetchRequest:request error:&error];
//Set if the name is avaliable or not
if ([objects count] == 0) {
bCanSave = YES;
} else {
bCanSave = NO;
}
}
It tells you exactly what the error is:
nil is not a legal NSManagedObjectContext parameter
That means that on this line:
newRecord = [NSEntityDescription insertNewObjectForEntityForName:entityName
inManagedObjectContext:context];
The variable context is nil. This means that your managedObjectContext method isn't working correctly. You don't show this so there's not much more we can add.
In application:didFinishLaunchingWithOptions: in appDelegate
/*initiate the managed Object Context */
CoreDataManager *coreDataManager = [CoreDataManager sharedDataManager];
coreDataManager.managedObjectContext = self.managedObjectContext;
where CoreDataManager is my core date manager which explicitly contains all the core data save, delete methods
Or
yourClassObject.managedObjectContext = self.managedObjectContext;
so context get initialized
The code is from Stanford iOS developing course's Photomania app. Basically I want to know when instances of Photo entity are actually fetched into memory (or context). Is that happen when the factory method defined here is called in a table view controller?
#interface Photo (Flickr)
+ (Photo *)photoWithFlickrInfo:(NSDictionary *)flickrInfo
inManagedObjectContext:(NSManagedObjectContext *)context;
#end
#implementation Photo (Flickr)
+ (Photo *)photoWithFlickrInfo:(NSDictionary *)flickrInfo
inManagedObjectContext:(NSManagedObjectContext *)context
{
Photo *photo = nil;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:#"Photo"];
request.predicate = [NSPredicate predicateWithFormat:#"unique = %#", [flickrInfo objectForKey:FLICKR_PHOTO_ID]];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"title" ascending:YES];
request.sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSError *error = nil;
NSArray *matches = [context executeFetchRequest:request error:&error];
if (!matches || ([matches count] > 1)) {
// handle error
} else if ([matches count] == 0) {
photo = [NSEntityDescription insertNewObjectForEntityForName:#"Photo" inManagedObjectContext:context];
photo.unique = [flickrInfo objectForKey:FLICKR_PHOTO_ID];
photo.title = [flickrInfo objectForKey:FLICKR_PHOTO_TITLE];
photo.subtitle = [flickrInfo valueForKeyPath:FLICKR_PHOTO_DESCRIPTION];
photo.imageURL = [[FlickrFetcher urlForPhoto:flickrInfo format:FlickrPhotoFormatLarge] absoluteString];
photo.whoTook = [Photographer photographerWithName:[flickrInfo objectForKey:FLICKR_PHOTO_OWNER] inManagedObjectContext:context];
} else {
photo = [matches lastObject];
}
return photo;
}
#end
The photo is loaded into memory when you call this method. CoreData probably does some caching such that subsequent fetches will not have to go to the storage backend, but this is definitely where the magic happens.
You should read up more on CoreData. It is a huge framework, but a solid understanding of it will take you a long way in designing efficient and sensible storage solutions for Cocoa apps.
This is kind of the "create photo" or "insert photo" method for the "database." So when the FlickrFetcher class goes out and retrieves photos, for every photo it retrieves this method is called.
This method first checks to see if the photos exists in the core data database, and if not adds it, and saves the managed object context.
So, technically, the Photo object is created in memory with [NSEntityDescription insertNewObjectForEntityForName: inManagedObjectContext:] method.
So I have an app I've written for the iPad, and I'd like to be able to allow users to insert images into their documents by selecting an image from an album or the camera. All that works great. Because the user might keep the document longer than they keep the image in an album, I make a copy of it, scale it down a bit, and store it in a core data table that is just used for this purpose.
I store the image like this:
NSManagedObjectContext* moc=[(ActionNote3AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSString* imageName=[NSString stringWithFormat:#"img%lf.png",[NSDate timeIntervalSinceReferenceDate]];
Image* anImage = [NSEntityDescription insertNewObjectForEntityForName:#"Image" inManagedObjectContext:moc];
anImage.imageName=imageName;
anImage.imageData=UIImagePNGRepresentation(theImage);
NSError* error=nil;
if(![moc save:&error]) {...
I sub-class NSURLCache, as suggested on Cocoa With Love, and ovverride cachedResponseForRequest thusly:
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
NSString *pathString = [[[request URL] absoluteString]lastPathComponent];
NSData* data = [Image dataForImage:pathString];
if (!data) {
return [super cachedResponseForRequest:request];
}
NSURLResponse *response =[[[NSURLResponse alloc]
initWithURL:[request URL]
MIMEType:[NSString stringWithString:#"image/png"]
expectedContentLength:[data length]
textEncodingName:nil]
autorelease];
NSCachedURLResponse* cachedResponse =[[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];
return cachedResponse;
}
I also make sure the app uses the sub-classed NSURLCache by doing this in my app delegate in didFinishLaunchingWithOptions:
ANNSUrlCache* uCache=[[ANNSUrlCache alloc]init];
[NSURLCache setSharedURLCache:uCache];
The method that returns the image data from the core data record looks like this:
+(NSData*)dataForImage:(NSString *)name {
NSData* retval=nil;
NSManagedObjectContext* moc=[(ActionNote3AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:#"Image" inManagedObjectContext:moc];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"imageName==%#", name];
[request setPredicate:predicate];
NSError* error=nil;
NSArray *array = [moc executeFetchRequest:request error:&error];
if ([array count]>0) {
retval=((Image*)[array objectAtIndex:0]).imageData;
}
return retval;
}
To insert the image into the web view, I have an html img tag where the name in src="" relates back to the name in the image table. The point of the NSURLCache code above is to watch for a name we have stored in the image table, intercept it, and send the actual image data for the image requested.
When I run this, I see the image getting requested in my sub-classed NSURLCache object. It is finding the right record, and returning the data as it should. However, I'm still getting the image not found icon in my uiwebview:
So Marcus (below) suggested that I not store the image data in a core data table. So I made changes to accomodate for that:
Storing the image:
NSString* iName=[NSString stringWithFormat:#"img%lf.png",[NSDate timeIntervalSinceReferenceDate]];
NSData* iData=UIImagePNGRepresentation(theImage);
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
NSString* fullPathToFile = [documentsDirectory stringByAppendingPathComponent:iName];
[iData writeToFile:fullPathToFile atomically:NO];
Retrieving the image:
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
NSString *pathString = [[[request URL] absoluteString]lastPathComponent];
NSString* iPath = [Image pathForImage:pathString];
if (!iPath) {
return [super cachedResponseForRequest:request];
}
NSData* idata=[NSData dataWithContentsOfFile:iPath];
NSURLResponse *response =[[[NSURLResponse alloc]
initWithURL:[request URL]
MIMEType:#"image/png"
expectedContentLength:[idata length]
textEncodingName:nil]
autorelease];
NSCachedURLResponse* cachedResponse =[[[NSCachedURLResponse alloc] initWithResponse:response data:idata] autorelease];
return cachedResponse;
}
In debug mode, I see that idata does get loaded with the proper image data.
And I still get the image-not-found image! Obviously, I'm doing something wrong here. I just dont know what it is.
So... What am I doing wrong here? How can I get this to work properly?
Thank you.
I would strongly suggest that you do not store the binary data in Core Data. Storing binary data in Core Data, especially on an iOS device, causes severe performance issues with the cache.
The preferred way would be to store the actual binary data on disk in a file and have a reference to the file stored within Core Data. From there it is a simple matter to change the image url to point at the local file instead.
So it turns out I was way overthinking this. When I write the HTML, I just write the path to the image in with the image tag. Works like a charm.
I would love to know why the solution I posed in my question did not work, though.
And, I did wind up not storing the images in a table.
I have been developing an iphone application using a domain model, and have put off the persistence aspect of the app until now. Core Data looks like a really good solution since I already have a well defined model but I am running into a snag with my existing unit tests.
Here is simple example of what I have now:
- (void)test_full_name_returns_correct_string {
Patient *patient = [[Patient alloc] init];
patient.firstName = #"charlie";
patient.lastName = #"chaplin";
STAssertTrue([[patient fullName] isEqualToString:#"charlie chaplin"], #"should have matched full name");
}
How can I make this work once my Patient object extends from NSManagedObject and uses #dynamic for the firstName and lastName properties?
Has anyone else run into this type of this with Core Data? Thanks.
You need to build a Core Data stack, either within each method or in -setUp and then tear it down. Using an NSInMemoryPersistentStore will keep things fast and in-memory for your unit tests. Add a #property (nonatomic,retain) NSManagedObjectContext *moc to your TestCase subclass. Then:
- (void)setUp {
NSManagedObjectModel *mom = [NSManagedObjectModel mergedModelFromBundles:[NSArray arrayWithObject:bundleContainingXCDataModel]];
NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
STAssertTrue([psc addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL] ? YES : NO, #"Should be able to add in-memory store");
self.moc = [[NSManagedObjectContext alloc] init];
self.moc.persistentStoreCoordinator = psc;
[mom release];
[psc release];
}
- (void)tearDown {
self.moc = nil;
}
Your test method then looks like:
- (void)test_full_name_returns_correct_string {
Patient *patient = [NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:self.moc];
patient.firstName = #"charlie";
patient.lastName = #"chaplin";
STAssertTrue([[patient fullName] isEqualToString:#"charlie chaplin"], #"should have matched full name");
}
assuming your entity is named Person. There was a memory leak in your version of the method, by the way; patient should be -release'd in the non-Core Data version (insertNewObjectForEntityForName:managedObjectContext: returns an autoreleased instance).
I used the answer above by Barry Wark, but I had to do some modifications to make it work with the current projects Xcode 5, iOS 7.
The property stayed the same:
#interface SIDataTest : XCTestCase
#property (nonatomic, retain) NSManagedObjectContext *moc;
#end
The setup had to actually had to change first of all to not release and secondly to provide a model URL.
- (void)setUp
{
[super setUp];
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"SimpleInvoice" withExtension:#"momd"];
NSManagedObjectModel *mom = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
XCTAssertTrue([psc addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL] ? YES : NO, #"Should be able to add in-memory store");
self.moc = [[NSManagedObjectContext alloc] init];
self.moc.persistentStoreCoordinator = psc;
}
Here is the example test case:
- (void)testCreateNew
{
Invoice *newInvoice = [NSEntityDescription insertNewObjectForEntityForName:#"Invoice" inManagedObjectContext:self.moc];
newInvoice.dueDate = [NSDate date];
NSString* title = [[NSString alloc] initWithFormat:#"Invoice %#", #112];
newInvoice.title = title;
// Save the context.
NSError *error = nil;
if (![self.moc save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
XCTFail(#"Error saving in \"%s\" : %#, %#", __PRETTY_FUNCTION__, error, [error userInfo]);
}
XCTAssertFalse(self.moc.hasChanges,"All the changes should be saved");
}
I set up an Entity using the Xcode .xcdatamodel file editor. I created an entity called Person, added a few attributes, then generated a .m file to represent it. That all works fine.
Now when I go to write a line of code like:
Person * person = (Person*)[NSEntityDescription
insertNewObjectForEntityForName:#"Person"
inManagedObjectContext:managedObjectContext];
And I get:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'Person''
I followed the Location example exactly though, step-for-step I believe, but I think I must have missed some kind of crucial "registration" step where I tell Xcode that my Person entity should be accessible.. Also I didn't have a way to "initialize" the managedObjectContext at all, the Location example doesn't seem to do that either.
The fact that you didn't set up the MOC is almost certainly the problem. Most specifically, it means you're probably not loading your MOM (Managed Object Model) that defines Person. Somewhere in your code you should have something like this:
managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];
And something like this:
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
And something like this:
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator: coordinator];
I'm just copying lines out of the AppDelegate of the Core Data template (what you get if you make a new application that uses Core Data).
If you have all that, make sure that your xcdatamodel is listed in your Compile Sources step of the build. And of course make sure that Person is actually the Entity name in your xcdatamodel. Entity name is not the same as Class, though they are often set to be the same.
You need the init of the Core Data
-(void)initCoreData{
NSError *error;
//Path to sqlite file.
NSString *path = [NSHomeDirectory() stringByAppendingString:#"/Documents/Level4.sqlite"];
NSURL *url = [NSURL fileURLWithPath:path];
//init the model
NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
//Establish the persistent store coordinator
NSPersistentStoreCoordinator *persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
if(![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error]){
NSLog(#"Error %#",[error localizedDescription]);
}else{
self.context = [[[NSManagedObjectContext alloc ] init ] autorelease];
[self.context setPersistentStoreCoordinator:persistentStoreCoordinator];
}
[persistentStoreCoordinator release];
}
You should check if the NSManagedObjectContext object is nil.
e.g.
if (self.managedObjectContext == nil) {
NSLog(#"NSManagedObjectContext is nil");
return nil;
}