I have problems with memory in my class methods.
I have created a class method which will fetch records from core data and return a NSArray.
These are the problem i face:
sometimes the data is returned properly, it works fine.
sometimes it returns a CFArray
a.how to deal with with type of array??
b.what does this type of array mean??
sometimes the array becomes a invalid object when returned to the class which called the method
But in all the ways NSArray inside the method has data. Why does it react in different ways every time? Is there any way to manage this problem?
Code snippet used:
+(NSArray *)retrieveEvents
{
NSArray *arrData;
NSError *error;
NSFetchRequest *fetch = [APPDEL.managedObjectModel fetchRequestTemplateForName:#"fetchEvents"];
arrData = [NSArray arrayWithArray:[APPDEL.managedObjectContext executeFetchRequest:fetch error:&error]];
return arrData;
}
Related
I have 3 entities that I generated with MOGenerator, I'd like to be able to get one of them back from their objectID
I tried this :
- (void)aMethod: (SpecialEntity1ID *)entityID
{
//This is a method from MagicalRecord but it doesn't matter(I think...).
NSManagedObjectContext *context = [NSManagedObjectContext MR_contextWithParent:[NSManagedObjectContext MR_defaultContext]];
SpecialEntity1 *entity1 = [context objectRegisteredForID:entityID]
//But this returns an NSManagedObject so it doesn't work...
}
Could someone help me get this object back with its ID ?
Since I don't know how to do it with the ID I'm currently working around it by making a method with an NSStringas a paramater instead of SecialEntity1ID that defines one of the attribute of this object (and is unique) and fetching the object.
I think getting back with his ID is better so any idea ?
You want to use existingObjectWithID:error: method of your NSManagedObjectContext and typecast the return type if you are 100% sure what it will be. I'd keep it generic i.e. let it return an NSManagedObject and then test its class elsewhere if you want to determine whether it belongs to a particular class.
- (Object*)retrieveObjectWithID:(ObjectID*)theID
{
NSError *error = nil;
Object *theObject = (Object*)[[NSManagedObjectContext contextForCurrentThread] existingObjectWithID:theID error:&error];
if (error)
NSLog (#"Error retrieving object with ID %#: %#", theID, error);
return theObject;
}
I have a coredata project that I'm trying to programmatically update a number.
I'm retrieving objects from CoreData and then storing it into an array.
Then, I'm looping through that array to see if the current user's IP is present in the database and trying to update the number of times accessed for that specific array.
The problem is, it's updating all the objects, not just the current object in the looped array.
First, I get the info from core data like so:
- (void)fetchRecords {
// Define our table/entity to use
NSEntityDescription *entity = [NSEntityDescription entityForName:#"IPAddr" inManagedObjectContext:managedObjectContext];
// Setup the fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
// Define how we will sort the records
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"ipDate" ascending:NO];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
[request setSortDescriptors:sortDescriptors];
// Fetch the records and handle an error
NSError *error;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (!mutableFetchResults) {
// Handle the error.
// This is a serious error and should advise the user to restart the application
}
// Save our fetched data to an array
[self setIpArray: mutableFetchResults];
}
Now, I'm trying to find if the current User IP is present in the fetched results, and if it's present, update the number of times accessed:
// see if the ip is present and update if necessary
-(void)ipPresent {
NSString * theCurrentIP = [self getGlobalIPAddress];
for (IPAddr *allips in ipArray)
{
if ([allips.ipNum isEqualToString:theCurrentIP]) {
NSLog(#"The IP %# was found.", theCurrentIP);
// update the ip
NSError *error = nil;
NSNumber *ipToUpdate = allips.ipAccess;
NSNumber *addIpAccess = [[NSNumber alloc] initWithInt:1];
NSNumber *updateIpAddress = [NSNumber numberWithFloat:([ipToUpdate floatValue] + [addIpAccess floatValue])];
[self.ipArray setValue:updateIpAddress forKey:#"ipAccess"];
if ([self.managedObjectContext save:&error]) { // write to database
NSLog(#"The IP Was Updated from %# to %#", ipToUpdate, updateIpAddress);
} else if (![self.managedObjectContext save:&error]) {
NSLog(#"failed with error: %#", error);
}
break;
} else {
NSLog(#"The IP %# was NOT found.", theCurrentIP);
}
}
}
I'm pretty sure the issue is with this line:
[self.ipArray setValue:updateIpAddress forKey:#"ipAccess"];
Again, it's updating ALL the entities and not just the one in the current loop.
Indeed. You are using the wrong method. self.ipArray is a NSMutableArray.
The method
- (void)setValue:(id)value forKey:(NSString *)key
is used for Key-Value Coding (which is what makes it work for Core Data objects), but when applied to an array, it will invoke setValue:forKey: on each entry in the array.
Now, you can see that you could also call setValue:forKey on the one single array element allips since its property is obviously KVC compliant -- otherwise you would be having a different problem, not see the values being set.
Note, that you could also just assign the property...
allips.ipAccess = updateIpAddress;
EDIT
Sorry, probably should have read slower... You do understand that you don't have to use a mutable array, right? You are not actually changing the array, just the elements in the array. An immutable collection means that the collection contents can not change, but when you have a pointer to an object, as long as that object is not immutable, you can still mutate its properties.
Thus, if you had an immutable array of Foo objects, you could do this...
for (Foo *foo in myImmutableArray) {
Bar *bar = [self getSomeNewBar];
[foo setBar:bar];
// If Foo is KVC compliant, you can do this too...
[foo setValue:bar for Key:#"bar"];
}
If, however, you call setValue:forKey on the array, it will be invoked for each element of the array. Note, that setValue:forKey is actually declared in the immutable NSArray.
EDIT
That comment was hard to read.
The core data object is just another object. It looks like you have subclassed it, and provided it with properties for the attributes. Just replace
[self.ipArray setValue:updateIpAddress forKey:#"ipAccess"];
with
[allips setValue:updateIpAddress forKey:#"ipAccess"];
or
allips.ipAccess = updateIpAddress;
Either of those should modify your core data object, as they would any object that had a read/write property named "ipAccess"
Assuming, of course, that I didn't read it wrong again... and allips is your core data object...
I create a custom object that has some properties like ID and Title,description etc...
And I add it to an array. (That array may contains more than 500 values).
And I use the following code to retrieve custom objects,
-(CustomObjects *)getObjectWithId:(int)id {
CustomObjects *objCustomObjects = nil;
for (CustomObjects *customObjects in arrayCustomObjects) {
if (customObjects.id == id) {
objCustomObjects = customObjects;
break;
}
}
return objCustomObjects;
}
But It has some performance problem, because I use the function to call on UIScrollview pinch.
How can I improve performance in fetching the objects?
thanks in advance,
A dictionary is better for this. The only catch is that you can’t have a NSDictionary with primitive int keys, so that you have to wrap the id in an NSNumber.
- (void) addCustomObject: (CustomObject*) obj {
NSNumber *wrappedID = [NSNumber numberWithInt:[obj idNumber]];
[dictionary setObject:obj forKey:wrappedID];
}
- (CustomObject*) findObjectByID: (int) idNumber {
NSNumber *wrappedID = [NSNumber numberWithInt:[obj idNumber]];
return [dictionary objectForKey:wrappedID];
}
A dictionary (also called hash table) does not have to go through all the values to find the right one, it has all the values arranged cleverly according to the keys so that it can jump to the right one or close to it. What you are doing with the array is called linear search and it’s not very efficient.
Better you can use NSDictionary with id as the key. You can easily fetch the object from the dictionary.
Is it Ok for your requirement?
You could use an NSPredicate that checks whether id equals the one you're looking for, and simply filter the custom objects using this predicate by calling filteredArrayUsingPredicate:.
To improve performance, I would try to postpone whatever you're trying to calculate by not directly calling the function that does the heavy work in your scroll view, but rather call [self performSelector:... withObject:nil afterDelay:0]; which postpones the calculation to the next runloop cycle. If you check if there's already a calculation scheduled before you call performSelector you should actually be able to reduce the frequency of the calculation while maintaining a crisp interface.
You must ditch the array in favor for a dictionary if you want to have fast lookups.
If you want to access objects both by key and index then you need to the objects around in two collections, and make sure they are in sync.
I have already done a helper class for this named CWOrderedDictionary. It's a subclass of NSMutableDictionary that allows for access to objects by both keys (as any dictionary do), and by index using methods identical to NSMutableArray.
My class is available to use for inspiration or as is from here: https://github.com/jayway/CWFoundation/
Use NSPredicate:-
You will receive the filtered array with the object that has the id you passed;
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"id == %#", id];
NSArray *filtered = [arrayCustomObjects filteredArrayUsingPredicate:predicate];
Instead of intjust use [NSNumber numberWithInt:] , i did some changes in your given code.
-(CustomObjects *)getObjectWithId:(NSNumber* )id {//changed int to NSNumber
CustomObjects *objCustomObjects = nil;
NSPredicate *bPredicate = [NSPredicate predicateWithFormat:#"SELF.id==%#",id];
NSArray *result = [array filteredArrayUsingPredicate:bPredicate];
//return filtered array contains the object of your given value
if([result count]>0)
objCustomObjects = [result objectAtIndex:0];
}
return objCustomObjects;
}
I'm writing a custom xml deserializer for an iphone app. As you can see below, I'm looping through all the list elements in the xml, I have debugged it, and with each loop there is a new and different element. The problem is that the xpath helper methods (there are similar ones to the one posted below, but for int and decimal) always returns the same value.
For example - 1st loop's xml "SomeValue" value will be "abc" and the helper method will return "abc", second item comes around and its xml "SomeValue" is "XYZ", but the helper method will still return "abc".
I'm new to iphone/objective c/memory managment so it could be any number of things. I just cant determine what the problem is :( could someone please offer some help?
-(void) deserializeAndCallback:(GDataXMLElement *)response
{
NSError * error;
NSArray *listings = [response nodesForXPath:#"//ListingSummary" error:&error];
NSMutableArray *deserializedListings = [[NSMutableArray alloc] init];
//loop through all listing elements, create a new listing object, set its values, and add
//it to the list of deserialized objects.
if(listings.count > 0)
{
for (GDataXMLElement *listingElement in listings)
{
Listing *list = [[Listing alloc] init];
//xpath helper function (shown below), just to get the value out of the xml
list.someValue = [QuickQuery getString:listingElement fromXPath:#"//SomeValue"];
[deserializedListings addObject:list];
}
}
if([super.delegate respondsToSelector: #selector(dataReady:)])
{
[super.delegate dataReady:deserializedListings];
}
}
+(NSString *) getString:(GDataXMLElement *)element fromXPath:(NSString *)xPath
{
NSError *error;
NSArray *result = [element nodesForXPath:xPath error:&error];
if(result.count > 0)
{
GDataXMLElement *singleValue = (GDataXMLElement *) [result objectAtIndex:0];
return singleValue.stringValue;
[singleValue release];
}
return nil;
[error release];
[result release];
}
EDIT: ok... I found a bit more info. Inside the helper function, the nodesForXpath method returns all the nodes from the entire xml, not just the current element I'm busy with. Does GDataXMLElement keep reference to its parent elements at all?
Example of what the xml looks like
<ListingSummary>
<SomeValue>abc</SomeValue>
</ListingSummary>
<ListingSummary>
<SomeValue>jhi</SomeValue>
</ListingSummary>
<ListingSummary>
<SomeValue>xyz</SomeValue>
</ListingSummary>
What you are seeing is correct behaviour for the XPath query you are using. You actually want a query relative to the current node, not the root of the document as you are doing.
See http://www.w3schools.com/xpath/
BTW + (NSString *)getString:(GDataXMLElement *)element fromXPath:(NSString *)xPath is a class method, not a static method.
You say that nodesForXPath: returns all the nodes from the whole document. Since you are calling that method with the same argument, #"//SomeValue", every loop, you get back the same array every time. This means that [result objectAtIndex:0] gives you the same object every time.
Also, as I mentioned in a comment, you should not be releasing singleValue, error, or result in your helper method. You don't own those and you're not responsible for their memory. On the other hand, since you create list using alloc, you do need to release it at the end of each loop; you are currently leaking a Listing object every pass.
It looks OK for me. Although the releases inside the getString:fromXPath: aren't necessary (you don't need to release parameters entered into a method or objects obtained from a NSArray. The proper way to release an object from a NSArray is removing it from the array, as for objects passed as a parameter, if you want to release it you should do it after you call the method.
The problem to your question must be somewhere else.
result.count should be [result count] since count is a method and not a property of NSArray
The goal is to have a singleton data controller class called FetchData.h/.m that pulls data using ObjectiveFlickr ( https://github.com/lukhnos/objectiveflickr ).
FetchData.m grabs the data with this:
OFFlickrAPIContext *context = [[OFFlickrAPIContext alloc] initWithAPIKey:YOUR_KEY sharedSecret:YOUR_SHARED_SECRET];
OFFlickrAPIRequest *request = [[OFFlickrAPIRequest alloc] initWithAPIContext:context];
// set the delegate, here we assume it's the controller that's creating the request object
[request setDelegate:self];
[request callAPIMethodWithGET:#"flickr.photos.getRecent" arguments:[NSDictionary dictionaryWithObjectsAndKeys:#"1", #"per_page", nil]]
and then implement the following delegate:
- (void)flickrAPIRequest:(OFFlickrAPIRequest *)inRequest didCompleteWithResponse:(NSDictionary *)inResponseDictionary;
Currently I have this code to save the NSDictionary as a property list to a file as an alternative to a singleton:
- (void)flickrAPIRequest:(OFFlickrAPIRequest *)inRequest didCompleteWithResponse: (NSDictionary *)inResponseDictionary{
if([inResponseDictionary writeToFile:#"inResponseDictionary.xml" atomically:TRUE])
{
NSLog(#"%#", [[NSFileManager defaultManager] fileExistsAtPath:#"inResponseDictionary.xml"]);
}
}
When I read this file back, I get Null. The file is read back as such:
NSDictionary *inResponseDictionary = [NSDictionary dictionaryWithContentsOfFile:#"inResponseDictionary.xml"];
NSDictionary *photoDict = [[inResponseDictionary valueForKeyPath:#"photos.photo"] objectAtIndex:0];
NSLog(#"%#", [photoDict count]);
Is there a better way to store this data from ObjectiveFlickr so that it can be accessed by other classes and view controllers? Or is there a better way to implement this in the View Controller.
What is in the returned NSDictionary? Are you sure they are all valid plist objects? The photo data might need to be modified (say, base 64 encoded into an array) before your write will work.
The docs for NSDictionary writeToFile: say
This method recursively validates that all the contained objects are property list objects (instances of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary) before writing out the file, and returns NO if all the objects are not property list objects, since the resultant file would not be a valid property list.
As for the singleton aspect - will you be making more than one of these calls at a time? Is there a need to persist the data? If no & no, just keep the dictionary in memory. If you have multiple calls happening at once, you'll need another layer of abstraction (some indexing) to put each call's results in it's own unique location. And that's not happening with your current implementation.