I have a NSMutableArray in an object.
In an object-method, I do something like this:
/* ... */
[[LRResty client] get:connectURL withBlock:^(LRRestyResponse *r) {
SBJsonParser *jsonParser = [SBJsonParser new];
NSDictionary *jsonResponse = [jsonParser objectWithString:[r asString]];
NSDictionary *permittedBases= [jsonResponse objectForKey:#"permittedBases"];
Database *database = [[Database alloc] init];
for (id key in permittedBases) {
/* ... */
[workingDatabases addObject:database];
}
}];
return workingDatabases;
At the return line, there are no objects in my array (anymore). I am aware of the fact, that the 'database'-objects are going out of scope. But I am saving them in the array.
Am I overseeing something?
If it is of any help, here is the header file:
#class Database;
#interface CommunicationHelper : NSObject {
NSMutableArray *workingDatabases;
}
// The function where the problem appears:
- (NSMutableArray *)getDatabasesForWebsite:(Website *)websiteIn;
#property(nonatomic,copy) NSMutableArray *workingDatabases;
#end
just allocate your workingDatabases (Mutable array) somewhere before using that array.
Once you allocate it,It will work fine.
I assume it's because [LRResty client] get: is asynchronous. The block is called when the connection is finished, i.e. after the call to return.
//Called first
[[LRResty client] get:connectURL
//Called second
return workingDatabases;
//Called later when the connection is finished
SBJsonParser *jsonParser = [SBJsonParser new];
NSDictionary *jsonResponse = [jsonParser objectWithString:[r asString]];
NSDictionary *permittedBases= [jsonResponse objectForKey:#"permittedBases"];
Database *database = [[Database alloc] init];
for (id key in permittedBases) {
/* ... */
[workingDatabases addObject:database];
}
Edit
Ajeet has a valid point too, ensure your array is initialized.
I used the LRResty framework for accessing a RESTful webservice. It was an odd thing anyways, so I switched to a way more rich-featured framework, called "ASIHTTP". I would recommend that to anyone who wants to use RESTful services (and more) on iOS
Related
I am trying to fetch object frames from given image using MKLKIT. But my code is getting crashed
MLKObjectDetectorOptions *options = [[MLKObjectDetectorOptions alloc] init];
#import <Foundation/Foundation.h>
#import <MLKitObjectDetection/MLKitObjectDetection.h>
#import <MLKitObjectDetectionCommon/MLKObjectDetector.h>
#import <MLKitObjectDetection/MLKObjectDetectorOptions.h>
#import <MLKitObjectDetectionCommon/MLKObject.h>
#import <MLKitVision/MLKVisionImage.h>
#import "MLKitObjectDetection.h"
#implementation MLObjectDetection
- (NSMutableArray*)detectFrame:(UIImage*)image{
NSMutableArray *frames = [NSMutableArray new];
// Multiple object detection in static images
MLKObjectDetectorOptions *options = [[MLKObjectDetectorOptions alloc] init];
options.detectorMode = MLKObjectDetectorModeSingleImage;
options.shouldEnableMultipleObjects = YES;
MLKObjectDetector *objectDetector = [MLKObjectDetector objectDetectorWithOptions:options];
MLKVisionImage *visionImage = [[MLKVisionImage alloc] initWithImage:image];
visionImage.orientation = image.imageOrientation;
NSError *error;
NSArray *objects = [objectDetector resultsInImage:visionImage error:&error];
if (error == nil) {
return frames;
}
if (objects.count == 0) {
// No objects detected.
}
for (MLKObject *object in objects) {
[frames addObject:[NSValue valueWithCGRect:object.frame]];
}
//TODO release memory
return frames;
}
#end
When your code crash, did you try to run your code inside Xcode and look into the console in the debug area to check what error message was printed out there? Usually that will give you some clue as to what led to the crash.
Based on your code, are you calling the detectFrame: method from the main UI thread? The synchronous MLKObjectDetector#resultsInImage:error: should never be called from the main UI thread. This is documented in its API reference. You can check out ML Kit's quickstart sample app here. It shows how to call both the synchronous MLKObjectDetector#resultsInImage:error: API and the asynchronous MLKObjectDetector#processImage:completion: API.
I have something along the line of this :
#implementation ImageLoader
NSMutableDictionary *_tasks;
- (void) loadImageWithURL:(NSURL *)url callback:(SMLoaderCallback)callback {
NSMutableArray *taskList = [_tasks objectForKey:urlString];
if (taskList == nil) {
taskList = [[NSMutableArray alloc] initWithCapacity:5];
[taskList addObject:callback];
[_tasks setObject:taskList forKey:urlString];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
dispatch_async(dispatch_get_main_queue(), ^{
UIImage *image = [[UIImage alloc] initWithData:data];
for (SMLoaderCallback cb in taskList) {
cb(image, nil);
}
[_tasks removeObjectForKey:url.absoluteString];
});
});
} else {
[taskList addObject:callback];
}
}
#end
In here, I'm trying to queue up image downloads to gain performance (as an exercise only). So I'm keeping a NSDictionary that maps an URL with an array of callbacks to be called whenever the data is downloaded.
Once the image is downloaded, I no longer need this array, so I remove it from the dictionary.
I would like to know if, in this code (with ARC enabled), my array along with the callbacks are correctly released when I call [_tasks removeObjectForKey:url.absoluteString].
If your project uses ARC and that dictionary is the only thing that is referencing to those values, yes. it will be remove permanently.
ARC keeps track of number of objects that is pointing to some other object and it will remove it as soon as the count reaches 0.
so adding to dictionary -> reference count += 1
removing from dictionary -> reference count -= 1
Somewhe
I've recently decided to move all my application data from plists to Core Data. This was pretty straightforward. I had a class with a couple properties I would read all my plist info to using a dictionary. This was mimicked by creating an entity with the same exact attributes. I then loaded the plist information into Arrays, and parsed them all, writing and save new entities to core data.
Sounds good no? Well, I thought to so. However, now that I'm reading it all back in, I've noticed some problems.
For one, when I go ahead and try to print off the properties of my object as follows:
for (CXStellarObject *obj in self.starsArray)
{
NSLog(#"Type: %#\n Language: %#\n Name: %#\n ImageName: %#\n Description: %#\n",obj.type,obj.language.label,obj.name,obj.imageName,obj.description);
}
I get this:
Type: star
Language: (null)
Name: Sirius
ImageName:
Description: <CXStellarObject: 0x7fbb0a58d5d0> (entity: CXStellarObject; id: 0xd000000000140000 <x-coredata://9E3F584C-3214-4A6A-B55A-B63D066A152B/CXStellarObject/p5> ; data: {
descriptor = "The brighest star visible from Earth, Sirius (Also known as Sirius A, or the Dog Star), is a bright white dwarf. It is part of the Canis Major Constellation. It is approximately 8.6 light years from o";
imageName = "";
language = "0xd000000000040002 <x-coredata://9E3F584C-3214-4A6A-B55A-B63D066A152B/CXLocalizationAsset/p1>";
name = Sirius;
type = star;
})
For one, my description isn't even complete. It cuts off at "from o", when it actually goes on longer in the plist. Next, name and type are repeated at the bottom of the printed results. I don't know why they're there.
Finally, what are all these addresses and other junk flanking the resulting data? I don't want that there, how did it get there?
You're probably going to need to see what I've got going on here, so I'll show you the Entity that is involved:
Here's how I wrote all these objects to Core Data:
-(void)writeAllArraysToCoreData
{
NSArray *starsArray = [self starsArray];
NSArray *planetsArray = [self planetsArray];
NSArray *moonsArray = [self moonsArray];
NSArray *allData = #[starsArray,planetsArray,moonsArray];
for (NSArray *array in allData)
{
for (NSDictionary *dict in array)
{
[self archieveCXStellarObjectWithLanguage:[dict valueForKey:#"Language"] Type:[dict valueForKey:#"Type"] Name:[dict valueForKey:#"Name"] ImageName:[dict valueForKey:#"ImageName"] Descriptor:[dict valueForKey:#"Description"]];
}
}
}
And finally, the method called in here that I defined:
-(void)archieveCXStellarObjectWithLanguage:(NSString *)languageCode Type:(NSString *)type Name:(NSString *)name ImageName:(NSString *)imageName Descriptor:(NSString *)descriptor
{
CXStellarObject *object = [NSEntityDescription insertNewObjectForEntityForName:#"CXStellarObject" inManagedObjectContext:self.managedObjectContext];
[object setLanguage:[self.supportedLanguageAssets valueForKey:languageCode]];
[object setType:type];
[object setName:name];
[object setImageName:imageName];
[object setDescriptor:descriptor];
// Add New Object to All Objects Array
[self.allStoredObjects addObject:object];
// Save Changes
[self saveContext];
}
And finally how I extracted them, and where this is going a bit awry (Don't worry, it's not a complicated method)
-(void)loadData
{
if (!self.allStoredObjects)
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"CXStellarObject" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *fetchResults = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (!fetchResults)
{
[NSException raise:#"Fetch Failed!" format:#"Reason: %#",[error localizedDescription]];
}
[self setAllStoredObjects:[NSMutableArray arrayWithArray:fetchResults]];
// Filter Arrays
NSPredicate *starPredicate = [NSPredicate predicateWithFormat:#"SELF.type == 'star'"];
[self setStarsArray:[fetchResults filteredArrayUsingPredicate:starPredicate]];
for (CXStellarObject *obj in self.starsArray)
{
NSLog(#"Type: %#\n Language: %#\n Name: %#\n ImageName: %#\n Description: %#\n",obj.type,nil,obj.name,obj.imageName,obj.description);
}
}
}
And that's it, thanks for taking the time to get this far. If you need any more information from me, just comment and I'll put it in ASAP.
Assuming your CXStellarObject object is a custom subclass of NSManagedObject, you need to override the description method for that object and write it to return formatted info about your managed object.
Something like this:
-(NSString *) description;
{
NSMutableString *result = [[NSMutableString alloc] init];
[result appendFormat: #" descriptor = %#\n", self.descriptor];
[result appendFormat: #" imageName = %#\n", imageName];
//And so on...
}
I suggest investigating Core Data "faults". Whenever you see references like that in your descriptions that is because the object is not in memory yet, only a stub of the object is. As soon as you touch the object Core Data will pull it into memory automatically and then the full values will be visible.
Further, it is common for long description calls to be clipped. If you want to see the full value, capture it in the debugger and call it via po.
As you can see, the code below isnt doing much (all commented out) more than enumerating over a set of files, however, my memory usage is growing to over 2 GB after 40 seconds of running the function below which is launched by pressing a button on the UI.
I can run the UI for hours, and before pressing the button, the memory usage does not exceed 8MB.
Given that ARC is turned on, what is holding on to the memory?
removed original code as the edit below made no differance.
EDIT:
Attempted #autoreleasepool{ dispatch_asyny ... } and permutations of that around the while and inside the while loop which had no effect.
Here is the code with autorelasepool added and cleaned up
-(void) search{
self.dict = [[NSMutableDictionary alloc] init];
NSFileHandle *fileHandle = [NSFileHandle fileHandleForWritingAtPath:#"/tmp/SeaWall.log"];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSString *bundleRoot = #"/";
NSFileManager *manager = [NSFileManager defaultManager];
NSDirectoryEnumerator *direnum = [manager enumeratorAtPath:bundleRoot];
NSString *filename;
while ((filename = [NSString stringWithFormat:#"/%#", [direnum nextObject]] ) && !self.exit) {
#autoreleasepool {
NSString *ext = filename.pathExtension;
if ([ext hasSuffix:#"so"] || [ext hasSuffix:#"dylib"] ) {
if (filename == nil || [NSURL URLWithString:filename] == nil) {
continue;
}
NSData *nsData = [NSData dataWithContentsOfFile:filename];
if (nsData != nil){
NSString *str = [nsData MD5];
nsData = nil;
[self writeToLogFile:[NSString stringWithFormat:#"%# - %#", [filename lastPathComponent], str]];
}
}
ext = nil;
} // end autoreleasepool
}
[fileHandle closeFile];
[self ControlButtonAction:nil];
});
}
The memory is not exactly leaked: it is very much ready to be released, but it never has a chance to be.
ARC builds upon the manual memory management rules of Objective-C. The base rule is that "the object/function that calls init owns the new instance", and the owner must release the object when it no longer needs it.
This is a problem for convenience methods that create objects, like [NSData dataWithContentsOfFile:]. The rule means that the NSData class owns the instance, because it called init on it. Once the value will be returned, the class will no longer need the object, and it would need to release it. However, if this happens before the callee gets a chance to retain the instance, it will be gone before anything had a chance to happen.
To solve this problem, Cocoa introduces the autorelease method. This method transfers the ownership of the object to the last autorelease pool that was set up. Autorelease pools are "drained" when you exit their scope.
Cocoa/AppKit/UIKit automatically set up autorelease pools around event handlers, so you generally do not need to worry about that. However, if you have a long-running method, this becomes an issue.
You can declare an autorelease pool using the #autoreleasepool statement:
#autoreleasepool
{
// code here
}
At the closing bracket, the objects collected by the autorelease pool are released (and possibly deallocated, if no one else has a reference to them).
So you would need to wrap the body of your loop in this statement.
Here's an example. This code "leaks" about 10 megabytes every second on my computer, because the execution never leaves the #autoreleasepool scope:
int main(int argc, const char * argv[])
{
#autoreleasepool
{
while (true)
{
NSString* path = [NSString stringWithFormat:#"%s", argv[0]];
[NSData dataWithContentsOfFile:path];
}
}
}
On the other hand, with this, the memory usage stays stable, because execution leaves the #autoreleasepool scope at the end of every loop iteration:
int main(int argc, const char * argv[])
{
while (true)
{
#autoreleasepool
{
NSString* path = [NSString stringWithFormat:#"%s", argv[0]];
[NSData dataWithContentsOfFile:path];
}
}
}
Creating objects in the loop condition is awkward for long loops because these are not picked up by the inner #autoreleasepool. You will need to get these inside the #autoreleasepool scope as well.
Returning
Whenever we return an object (maybe to Swift), we need to register into nearest #autoreleasepool block (by calling autorelease method to prevent memory-leak, according to ownership-rules), but nowadays ARC does that automatically for us;
Whenever ARC disabled; after using alloc and/or init, call autorelease manually, like:
- (NSString *)fullName {
NSString *string = [[[NSString alloc] initWithFormat:#"%# %#",
self.firstName, self.lastName] autorelease];
return string;
}
Memory needs to be released by an autorelease pool.
Otherwise it will be locked up as you are experiencing and it will leak.
In your loop put:
#autoreleasepool { /* BODY */ }
I am creating a basic guessing game in iOS for my kids, and I think there are some fundamental gaps in my understanding of how I should be creating and releasing objects throughout the lifecycle of the app. I have been reading up on retain and release cycles but I think my issue is more to do with the fundamental architecture of the app and how I may be poorly trying to instantiate and then kill a few key objects of the app.
The problem centers around two specific classes.
I have a game class, which I have designed to hold all the information that the game requires to run. When it is init-ed, it holds all instance variables that point to arrays that hold strings such as the various clues, etc. It's basically a container for all the data that the game requires.
I have a game view controller, that creates and an instance of the game class and queries it so as to present on screen the various elements contained with the game object.
This works perfectly the fine. When the user starts a new game, a new instance of the game class is allocated and init-ed and away they go.
The issue comes in when I come to generate a new game. This happens a number of ways. Either The user finishes the game and starts another one or the user quits the current game and then starts a new one.
In my thinking, I would just release the game object and alloc and init a new one. However, I notice running on the device and looking through the profiler, that the game object isn't released at all.It's still, there and each instantiation of the game creates a new game object with the old one still sitting there with no pointers to it.
Fiddling around with the code, I noticed that I did not implement a dealloc method in the Game class...but when I try to do that, the app crashes, I suspect because I am trying to release a previously released object.
Ideally what I am trying to do is get rid of the old Game object, or replace the old one (overwrite) with a new one each time a new game is started.
However, is this approach wrong? Should I be doing it a completely different way? Such as only ever creating a single instance of the game class and rewriting a method inside that class so as to generate a new set of clues, etc everytime a new game starts and the GameViewController tells it to?
Is there a 'best practice' way to do this?
So you've got an idea of what I am doing, code is below for the GameViewController, where an instance of the Game class is created:
#import "GameViewController.h"
#implementation GameViewController
#synthesize game = _game;
-(void)startNewGameOfLevel:(NSInteger)level
{
if(!_game)
{
Game *g = [[Game alloc]initGamewithLevel:level];
[self setGame:g];
[g release]; g = nil;
}
[self set_currentlevel:[_game _currentLevel]];
// set up popover to show the rounds goal letter
[self setUpPopOver];
}
-(void)quitTheCurrentGameAndStartNewGame
{
[_game release]; _game = nil;
[self clearGamePlayingField];
animationStepIndex = 0;
[self startNewGameOfLevel: _currentlevel];
}
Game class (abridged) with the designated initializer of the Game class:
#import "Game.h"
#implementation Game
#synthesize arrayOfLowerCaseLetters = _arrayOfLowerCaseLetters;
#synthesize arrayOfPhrases= _arrayOfPhrases;
#synthesize goalLetter = _goalLetter;
#synthesize goalPhrase = _goalPhrase;
#synthesize gameLetterPool = _gameLetterPool;
#synthesize _indexForGoalLetter, _numberOfLevelsInGame, _currentLevel, _numberOfWhackHoles, _numberOfLettersInGameLetterPool;
-(id)initGamewithLevel:(NSInteger)level
{
[super init];
//create an array of lower case letters. These will
//contain the full alphabet of all possible letters
NSArray *arrayOfLCLetters = [[NSArray alloc] initWithObjects:#"a", #"b", #"c", #"d",#"e", #"f", #"g", #"h", #"i", #"j", #"k", #"l", #"m", #"n", #"o", #"p", #"qu", #"r", #"s", #"t", #"u", #"v", #"w", #"x",#"y", #"z",#"ch", #"sh", #"th", nil];
[self setArrayOfLowerCaseLetters: arrayOfLCLetters];
[arrayOfLCLetters release];arrayOfLCLetters = nil;
//create an array of phrases.
// These must correspond with each of the letters. e.g. a = apple.
NSArray *phrases= [[NSArray alloc ] initWithObjects:
#"apple",
#"butterfly",
#"cat",
#"dog",
#"egg",
#"frog",
#"ghost",
#"horse",
#"igloo",
#"jam",
#"kite",
#"leaf",
#"moon",
#"nut",
#"orange",
#"pig",
#"queen",
#"rabbit",
#"snake",
#"tree",
#"umbrella",
#"van",
#"water",
#"x-ray",
#"yak",
#"Zebra",
#"chair",
#"shoes",
#"thumb",
nil];
[self setArrayOfPhrases:phrases];
[phrases release]; phrases = nil;
//choose a random number to be the index reference for
// each goal letter and goal phrase.
[self set_indexForGoalLetter:(arc4random()%[_arrayOfLowerCaseLetters count])];
NSLog(#"index for goal letter is:, %i", _indexForGoalLetter);
//set Goal letter and goal phrase
[self setGoalLetter: [_arrayOfLowerCaseLetters objectAtIndex: _indexForGoalLetter]];
[self setGoalPhrase: [_arrayOfPhrases objectAtIndex:_indexForGoalLetter ]];
//set current level
[self set_currentLevel: level];
//[self set_currentLevel: 2];
//set number of whackholes by level
[self set_numberOfWhackHoles: [self numberOfWhackHolesByLevel:_currentLevel]];
//generate size of Letter pool by level
[self set_numberOfLettersInGameLetterPool:[self numberOfLettersInLetterPoolbyLevel:_currentLevel]];
////////////////////////////
/// Game letter pool
///////////////////////////
//set up array ton hold the pool of letters
NSMutableArray *gp = [[NSMutableArray alloc] initWithCapacity:_numberOfLettersInGameLetterPool];
[self setGameLetterPool: gp];
[gp release];gp = nil;
//add the goal letter to this pool
[_gameLetterPool addObject:_goalLetter];
int i = 1;
while (i < _numberOfLettersInGameLetterPool) {
NSString *letter = [_arrayOfLowerCaseLetters objectAtIndex:(arc4random()%[_arrayOfLowerCaseLetters count])];
if ([_gameLetterPool containsObject:letter] == false)
{
[_gameLetterPool addObject:letter];
i++;
}
}
NSLog(#"********** Game created ***************");
NSLog(#"pool of letters is: %#", [_gameLetterPool description]);
NSLog(#"****************************************");
NSLog(#"current goal letter is: %#", _goalLetter);
NSLog(#"****************************************");
NSLog(#"current goal phrase is: %#", _goalPhrase);
NSLog(#"****************************************");
return self;
}
-(void)dealloc
{
[super dealloc];
[_arrayOfLowerCaseLetters release]; _arrayOfLowerCaseLetters = nil;
[_arrayOfPhrases release]; _arrayOfPhrases = nil;
[_goalLetter release];_goalLetter = nil;
[_goalPhrase release]; _goalPhrase = nil;
[_gameLetterPool release];_gameLetterPool = nil;
}
The number one problem is that [super dealloc] must be the absolute last thing you do in -dealloc. This is because it is the dealloc method in NSObject that actually frees the memory, so by the time you get back to it, your instance variable pointers may already be garbage.
Other issues:
In init, do self = [super init]; The super object is allowed to return a different self pointer on init.
startNewGameOfLevel: and quitTheCurrentGameAndStartNewGame should use the property, not the bare instance variable.
-(void)startNewGameOfLevel:(NSInteger)level
{
if(![self game])
{
Game *g = [[Game alloc]initGamewithLevel:level];
[self setGame:g];
[g release]; g = nil;// g = nil, not necessary when it's about to go out of scope
}
[self set_currentlevel:[[self game] _currentLevel]]; // don't use _ to start methods - Apple reserves this convention
// set up popover to show the rounds goal letter
[self setUpPopOver];
}
-(void)quitTheCurrentGameAndStartNewGame
{
[self setGame: nil];
[self clearGamePlayingField];
animationStepIndex = 0;
[self startNewGameOfLevel: _currentlevel];
}
There are probably other issues in the body of your code - make sure you build with static analysis enables - it will catch many of them.