Dont why this is happening I have a method getOutage which returns an array of managed objects
NSArray *fetchedOutages = [context executeFetchRequest:fetchRequest error:&error];
if (error) {
NSLog(#"Error in Core Data: %#", [error description]);
}
return fetchedOutages;
when I try to copy this array to listOutage (this is a property)
#property (nonatomic, retain) NSArray *listOutage
I tried to copy this array like this in didRowSelectMethod like this
if (listOutage) {
NSLog(#"Its there");
[listOutage release];
}
listOutage=[[NSArray alloc] initWithArray:[self getOutage]];
I tried various other methods but all of then are failing.
This getoutage method returns 5 objects five objects got copied in listOutage but when I try to access the listOutage elements they are displayed as 'out of scope'
Please help me to overcome this I have to pass this to next ViewController.
Thanks in advance
when there is a property, use 'self.property' instead of 'property' that way, when somebody else reads your code it is more obvious if you mean an ivar or a property.
if you use self.property, you do not need to write
if (listOutage) {
NSLog(#"Its there");
[listOutage release];
}
listOutage=[[NSArray alloc] initWithArray:[self getOutage]];
instead, just write
NSArray newListOutage=[[NSArray alloc] initWithArray:[self getOutage]];
self.listOutage = newListOutage;
[newListOutage release];
the release and retain will be handled by the get/set method generated by the #synthesize property.
Related
I want to be able to access an array of objects in my iPhone application. The array of objects is populated in the appDelegate of my application and I want to be able to access the array in one of my View Controllers.
I currently set up the array in my appDelegate.h file as follows:
NSArray *listObjArray;
#property (nonatomic, retain) NSArray *listObjArray;
I then populate it with some Strings like this in the AppDelegate:
listObjArray = [NSArray arrayWithObjects:#"Hello", #"How", #"are", nil];
NSLog(#"Array size = %i", [listObjArray count]);
It is synthesized and also released in dealloc. The NSLog returns the correct count here.
In my ViewController class I import the appDelegate like this:
#import "MyaAppDelegate.h"
I then access my appDelegate and the NSArray like this and try to Log the count in my View Controller:
MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication]
delegate];
NSLog(#"Before array set");
NSArray *newArray = [appDelegate listObjArray];
NSLog(#"After array set");
NSLog(#"array count = %i", [newArray count]);
NSLog(#"After array count");
The logging here gets to "After array set" and then I get "EXC_BAD_ACCESS" on the line where I try to print the count from the array in the View Controller.
The printing of the count works fine from the appDelegate and setting the newArray as the array from the delegate appears to work yet I cant do anything with it then.
Can anyone see what I am doing wrong?
I think your array declaration should be:
NSArray *newArray = [[NSArray alloc] initWithArray:appDelegate.listObjArray]
Be sure to release it after you are done! Though I'm not sure why you want to declare the new array, you could just do:
NSLog(#"array count = %i", [appDelegate.lstObjArray count]);
Hope this helps!
-Karoly
You have a memory issue: listObjArray = [NSArray arrayWithObjects:#"Hello", #"How", #"are", nil]; sets the instance variable directly. Shortly after this line the array gets released again, which results in you accessing a bad memory location in NSArray *newArray = [appDelegate listObjArray];, since it has been freed.
Use self.listObjArray = ... instead when populating the array. This will properly retain the object for you.
Please use the getter if it is sythesized. Since you are not using the getter, it is giving you bad memory access.
Also you should use retain or copy if you want to retain it or copy it. Else both newArray and listObjectArray will point to same memory location causing bad behavior.
NSArray *newArray = [[appDelegate getListObjArray] retain];
Try this
self.listObjArray = [NSArray arrayWithObjects:#"Hello", #"How", #"are", nil];
Allocation should be made on the getter.
After a ASIFormDataRequest , i create a temporary NSMutableArray *resultArray from the JSON then add it to a defined NSMutablearray *myData
-(void)viewDidLoad{
myData = [[NSMutableArray alloc] init];
//request that calls gotInfo method
}
-(void)gotInfo:(ASIFormDataRequest *)request{
NSString *responseString = [request responseString];
NSMutableArray *resultArray = [responseString yajl_JSON];
[myData addObject:resultArray];
}
-(IBAction)doSomethingWithData:(id)sender{
//something with myData
}
but when i try to call myData from outside of the gotInfo: method, i get bad access errors and when i inspect myData outside of the method, it shows a kern_protection_failure. So i'm guessing that outside of the method, the resultArray is obviously released, but it's also released from myData since the object inside myData is sharing the same memory location?
I also tried
-(void)gotInfo:(ASIFormDataRequest *)request{
NSString *responseString = [request responseString];
[myData addObject:[responseString yajl_JSON]];
}
How do I preserve myData??
in my header file:
#import <UIKit/UIKit.h>
#class ASIFormDataRequest;
#interface EventsTableController : UITableViewController <UITableViewDataSource>{
NSMutableArray *myData;
}
-(void)gotInfo:(ASIFormDataRequest *)request;
UPDATE:
so in the gbd, the myData is allocated as 0x5e96560 so i did
po 0x5e96560
and then i get the EXC_BAD_ACCESS with the reason being KERN_PROTECTION_FAILURE at address: 0x00000009
but if i do
po [[0x5e96560 objectAtIndex:0] objectForKey:#"key"]
then i get the value! whyyyyyy?
#property(nonatomic,retain) NSMutableArray *myData
and create the object
self.myData = [[NSMutableArray alloc] init];
and
// and i assume your resultArray is a mature NSMutableArray object
[self.myData addObject:resultArray];
The best way of using copy I can think of, is to always set NSString properties to "copy" instead of retain. That way you get more accurate readings from the Leaks instrument if you mess up and forget to release a string an object is holding onto. Other uses of copy need to be more carefully thought out.
NOTE : You are responsible to release myData after no use of that variable.
You dont really have any way to correctly access myData as you declare it as a member inside of EventsTableController, but you dont set the #property for it, and do not synthesize it either. By synthesizing it in your EventsTableController.m file you are telling xcode to generate the getter/setters you need to correctly touch myData, which is where your program seems to be failing. If you do this, this should solve your problem.
-Karoly
Except for the different name of your ivar (mienVar vs. myVar), I don't see a problem. Some other code must be releasing your ivar, or you are accessing it before viewDidLoad has the opportunity to actually create the array (I bet it is the latter).
I think you should put the code in viewDidLoad in your initialization method instead. Don't forget to release the array in dealloc.
You could, of course, also write your own myData getter method, doing lazy initialization, instead of creating it in the init method:
- (NSMutableArray *) myData
{
if (!myData)
myData = [[NSMutableArray alloc] init];
return myData;
}
Note that now, you should access self.myData if you want to use it.
I think the NSString yajl_JSON category can return an array or a dictionary - you might need to inspect the type of the result array on the line below as it may be an NSDictionary:
NSMutableArray *resultArray = [responseString yajl_JSON];
IF you are treating it as an array when its a dictionary that might be causing your problems.
(relevant code from the NSObject+YAJL category below)
YAJLDocument *document = [[YAJLDocument alloc] initWithData:data parserOptions:options error:error];
id root = [document.root retain];
[document release];
return [root autorelease];
(and in YAJLDocument object)
#interface YAJLDocument : NSObject <YAJLParserDelegate> {
(id root_; // NSArray or NSDictionary
The following is implemented as a class method in a category on one of my managed object entities, with a bunch of other operations:
+ (NSArray*)newArrayOfAllOtherBibs
{
NSManagedObjectContext* moc = [(MyAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init];
NSString* entityName = NSStringFromClass([self class]);
NSEntityDescription* entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:moc];
[fetchRequest setEntity:entity];
NSError* error;
NSArray* items = [moc executeFetchRequest:fetchRequest error:&error];
[fetchRequest release];
NSMutableArray* bibArray = [NSMutableArray array];
for(int i = 0; i < [items count]; i++)
{
Person* person = [items objectAtIndex:i];
if(![person.isSelf isEqualToString:#"YES"])
{
// crash here!
if([person.bib length] > 0)
// crash here!
[bibArray addObject:person.bib];
}
}
return [bibArray retain];
}
So it is supposed to look at all entities for Person, returned for a very simple fetch, and add all that are not marked as "self" (attribute isSelf, type NSString) to a new array which is returned to the caller. All the other methods for add/delete/find matching are working well.
Using
NSString* entityName = NSStringFromClass([self class]);
is an attempt to make the function more generic so I can cut&paste these functions for other entities as required with less editing.
Person looks like this:
#interface Person : NSManagedObject
{
}
#property (nonatomic, retain) NSString * bib;
#property (nonatomic, retain) NSString * isSelf;
[...]
#end
Question is, what could explain EXC_BAD_ACCESS on the line marked? Analyzer shows nothing. At that point person is clearly OK or I would expect it to die earlier, on accessing .isSelf. (It could be made a boolean but I find having two kinds of boolean, one BOOL and one NSNumber, error prone). If person.bib is nil then calling length on it should still return 0 right? But it can't be nil anyway since "bib" is the key for these entities and one is never created without it. At this stage nothing has been deleted from the store, it's a fresh store that has been saved since last addition.
The cause of the problem:
NSDictionary *resultDict = [responseString JSONValue];
NSString* bib = [resultDict objectForKey:#"bib"];
person = [NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:moc];
person.bib = bib;
[... lots of stuff setting up relationships for person etc.]
NSError *error;
if (![moc save:&error])
{
NSLog(#"Core Data Save error %#, %#", error, [error userInfo]);
}
The fix:
person.bib = [bib copy];
seems like the bib string was not valid at the time the Person entity was saved.
The best thing to do is set NSZombieEnabled in the executable and debug it from there. This way you'll be able to see what is causing the problem.
If you are loading some vars lazily make sure you set them to nil when you release them because if not next time when accessed them. They will not be "skipped", you app will try to use them but since they are not pointing to a valid object it fails and gives you errors like EXC_BAD_ACCESS
Person.bib may not have been loaded yet.
Did you leave the bib property defined as #dynamic and not #synthesize?
Did you override the bib accessor method? If so your override needs to be KVO friendly.
I'm facing a strange problem with NSUsrDefaults. Whenever I'm fetching the data from NSUserDefaults, it's getting populated temporarily. I'm fetching it into viewDidLoad where it's fetched.
-(void)viewDidLoad{
companies = [NSMutableArray array];
oldCompanies = [[NSUserDefaults standardUserDefaults] arrayForKey:#"companyData"];
if( companies )
{
for( NSData *data in oldCompanies )
{
companyObj = (Company*) [NSKeyedUnarchiver unarchiveObjectWithData:data];
[companies addObject:companyObj];
}
}
}
But outside viewDidLoad, whenever I try to access the data, the array "oldCompanies" as well as "companies" are shown "nil".
EDIT:
I'm encoding my Company object in a class which subclasses NSCoding like shown below but not allocating or retaining the properties anywhere. Can this be the catch?
- (void)encodeWithCoder:(NSCoder *)encoder
{
//Encode properties, other class variables, etc
[encoder encodeObject:self.companyId forKey:#"id"];
[encoder encodeObject:self.companyTitle forKey:#"title"];
[encoder encodeObject:self.companyImage forKey:#"image"];
}
- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if( self != nil )
{
//decode properties, other class vars
self.companyId = [decoder decodeObjectForKey:#"id"];
self.companyTitle = [decoder decodeObjectForKey:#"title"];
self.companyImage = [decoder decodeObjectForKey:#"image"];
}
return self;
}
Can anybody please help?
Thanx in advance.
+array creates an autoreleased array - if you want to take ownership of it per the memory management rules then you need to retain it:
[companies retain];
Or create it so that it isn't autoreleased:
companies = [[NSMutableArray alloc] init];
Or, better, let declared properties do that for you:
// interface, property declaration:
#property(retain, readwrite) NSMutableArray *companies;
// implementation:
#synthesize companies;
// ... using it:
self.companies = [NSMutableArray array];
You are not retaining the array, when you dont do an alloc, or a retain when instatiating an object you get an autoreleased object, in your example companies is autoreleased and is why you cant access it anymore at a later point you should either alloc it
[[NSMutableArray alloc] init] or retain it [NSMutableArray array] retain]...either way refer to memory managment guide to learn about objective-c memory managment memory managment ref
Are you trying to access the data before the view is loaded?
Objective-C doesn't reset your pointers for you. If the array isn't "persisted", then the pointer will point to garbage.
I'm new to Objective C and was wondering if anyone can help me.
I am using core data with a sqlite database to hold simple profile objects which have a name and a score attribute (both of which are of type NSString).
What I want to do is fetch the profiles and store them in an NSData object, please see my code below:
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"GamerProfile" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"Name" ascending:YES];
NSArray *sortDecriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDecriptors];
[sortDescriptor release];
[sortDecriptors release];
NSError *error;
NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:items];
[self SendData:data];
[fetchRequest release];
When I run the code I'm getting the error "Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[GamerProfile encodeWithCoder:]: unrecognized selector sent to instance 0x3f4b530'"
I presume I have to add an encodeWithCoderClass to my core data NSManagedObject object (GamerProfile) but I'm not sure how to do this even after reading the documentation, My attempt at doing this is below. I'm not sure if I'm going along the right lines with this as get a warning stating "NSManagedObject" may not respond to '-encodeWithCoder'"
I would really, really appreciate it if someone could point me in the right direction!!
Thanks
C
Here is the code for my GamerProfile (CoreData NSManagedObject Object) with my attempt at adding an encodeWithCoder method...
Header File
#import <CoreData/CoreData.h>
#interface GamerProfile : NSManagedObject <NSCoding>
{
}
#property (nonatomic, retain) NSString * GamerScore;
#property (nonatomic, retain) NSString * Name;
- (void)encodeWithCoder:(NSCoder *)coder;
#end
Code File
#import "GamerProfile.h"
#implementation GamerProfile
#dynamic GamerScore;
#dynamic Name;
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:GamerScore forKey:#"GamerScore"];
[coder encodeObject:Name forKey:#"Name"];
}
I got this to work. Here's how.
First create an NSValueTransformer like so:
ArrayToDataTransformer.h
#interface ArrayToDataTransformer : NSValueTransformer {
}
#end
ArrayToDataTransformer.m
import "ArrayToDataTransformer.h"
#implementation ArrayToDataTransformer
+ (BOOL)allowsReverseTransformation {
return YES;
}
+ (Class)transformedValueClass {
return [NSData class];
}
- (id)transformedValue:(id)value {
//Take an NSArray archive to NSData
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:value];
return data;
}
- (id)reverseTransformedValue:(id)value {
//Take NSData unarchive to NSArray
NSArray *array = (NSArray*)[NSKeyedUnarchiver unarchiveObjectWithData:value];
return array;
}
#end
The above is your interface to NSManagedObject, now create one that use it, for example:
Array.h
#import <CoreData/CoreData.h>
#class Arrays;
#interface Array : NSManagedObject
{
}
#property (nonatomic, retain) id myArray;
#property (nonatomic, retain) Arrays * arrayOfArrays;
#end
Array.m
#import "Array.h"
#import "Arrays.h"
#implementation Array
#dynamic myArray;
#dynamic arrayOfArrays;
#end
In the xcdatamodel, Array needs myArray Attributes set as Optional (usually always checked), and Type is: Transformable, and Value Transformer Name: ArrayToDataTransformer
Now you can use it;
NSMutableArray* positionArray;
positionArray = [[NSMutableArray alloc] arrayWithCapacity:[myArray count]];
for(NSArray *pos in myArray) {
[positionArray addObject:[NSString stringWithFormat:#"%#",pos]];
}
NSLog(#"ArrayCtrl : positionArray cnt = %d",[positionArray count]);
//Now add the positionArray to CoreData using the setValue & myArray Key
Array *array = (Array*)[NSEntityDescription insertNewObjectForEntityForName:#"Array" inManagedObjectContext:self.managedObjectContext];
[array setValue:positionArray forKey:#"myArray"];
[myArrays setMyArrays:array];
[self saveAction:array];
[positionArray release];
To retrieve the data from CoreData:
using a one-to-one relationship, thus myArrays points to just one array element
NSArray *positionArray = [myArrays.array valueForKey:#"myArray"];
If you are using a one-to-many, and things are named as above, you'll get back an NSSet.
Core Data should store the Array as a Blob in the database, and a large Array can be written very quickly, say one with 3,500 objects takes less than a second. The performance is comparable to how UIImage is stored and retrieved using pretty much the same concepts. The retrieval I think is even faster.
The alternative is to write each value of the Array individually into Core Data. For this you need to create the appropriate NSManageObject, but beware that you'll have to save 3,500 times for each array value, and for 3,500 items, this will take 20 to 30 seconds.
Thus the above method is great for writing large arrays into CoreData in one shot, and retrieving them also in one shot.
Spent a few hours on this one, was about to give up, and then I saw the light!
NSManagedObject and NSCoding really do not play well together. Consider this answer to a similar question for background and a possible solution.