I have a UIView that has many instances and each one of them has a UIRecognizer.
When on of them is tapped I want to remove all the recognizers of the others.
What I want it to get all the instances of the class and remove their recognizes.
I know ManagedObjects has [Entity allObjects];
How can I create my "all objects" class method ?
I have two ideas:
1/ Create a class array with all the instances static NSArray* instances;, register them when initializing, unregister when deallocating. The array should have only weak references, otherwise they will never be deallocated.
2/ NSNotification. All instances can wait for a notification and if you tap, you send the notification.
First I'd say whatever you're trying to accomplish can likely be better accomplished with NSNotificationCenter, that said, if you still need to do this, the following will work and will be ARC compliant.
In your .h add this:
+(NSArray *)allInstances;
Then, add this to the bottom of your class's .m:
-(id)init {
//Note, I suppose you may need to account for exotic init types if you are creating instances of your class in non-traditional ways. I see in the docs that initWithType: exists for example, not sure what storyboard calls
self = [super init];
[[self class] trackInstance:self];
return self;
}
-(void)dealloc {
[[self class] untrackInstance:self];
}
static NSMutableArray *allWeakInstances;
+(void)trackInstance:(id)instance {
if (!allWeakInstances) {
allWeakInstances = [NSMutableArray new];
}
NSValue *weakInstance = [NSValue valueWithNonretainedObject:instance];
[allWeakInstances addObject:weakInstance];
}
+(void)untrackInstance:(id)instance {
NSValue *weakInstance = [NSValue valueWithNonretainedObject:instance];
[allWeakInstances removeObject:weakInstance];
}
+(NSArray *)allInstances {
NSMutableArray *allInstances = [NSMutableArray new];
for (NSValue *weakInstance in allWeakInstances) {
[allInstances addObject:[weakInstance nonretainedObjectValue]];
}
return allInstances.copy;
}
Then when you need all instances of the class, just call [Class allInstances];
If you just need to find all instances for debugging purposes, you can use the Allocations instrument and change the Recorded Types to only your class. This will give you a dandy list of all your objects. You can then interact with them using lldb by using their address.
If they're all subviews of the same view, you could iterate over parentView.subviews and find them that way. Something like this:
for (UIView *v in parentView.subviews) {
if ([v isKindOfClass:[MyViewClass class]]) {
// remove recognizer here
}
}
Another, more efficient, option would be to have a flag in your view controller that you set when the first recognizer is triggered and use to short-circuit any future recognizer handler calls. Something like this:
#property (nonatomic) BOOL shouldRespondToEvent;
#synthesize shouldRespondToEvent=_shouldRespondToEvent;
- (void)viewDidLoad {
[super viewDidLoad];
self.shouldRespondToEvent = YES;
// other viewDidLoad stuff here
}
- (void)gestureHandler:(UIGestureRecognizer*)recognizer {
if (!self.shouldRespondToEvent)
return;
self.shouldRespondToEvent = NO;
// rest of handler code here
}
Related
Now I am developing an iOS application which works like this:
User scans QR code,
App searches for a specific key - > value,
it gives out a value to the user.
Currently I have two ViewControllers - the main and "value" ViewController, which is inherited from main. The problem is that if I create NSDictionary in main VC it is not visible in "value" VC. Main VC gives only the string (QR code, the key) through the segue. So, the value VC has to search for key and display the value.
What I ask is some kind of global variable or one DataSource visible across the whole app. Of course, I can implement NSDictionary initialisation inside value ViewDidLoad method and it will work, but this is not the point. New modules are to be added there and the variable has to be global. I googled a lot and got the idea that singleton pattern can be helpful here. I tried to implement it, but no idea how to do. Do I need it, or it is too complex for this kind of DataSource?
Thank you!
The basic idea is, you will still need to #include the header file of the place where this dictionary will be. The solution that Naveen proposes means that you will be including the header for the app delegate wherever you want to access it. Whether to use the app delegate for this purpose or not is kinda grayish. Some people often do this, some say its a bad use of it.
The singleton approach means that you will create a class, that will always contain the same information since the init method will return object that was previously created.
For the singleton aproach, imagine I have a database manager class. So in the header of this class (the DatabaseManagerSingleton.h) ill have this:
#interface DatabaseManager : NSObject
+ (DatabaseManager*)sharedInstance;
// Your dictionary
#property (nonatomic,strong) NSMutableDictionary* someDictionary;
The implementation will look like this: (check how "sharedInstance" initializes the object)
#implementation DatabaseManager
#pragma mark - Singleton Methods
+ (DatabaseManager*)sharedInstance {
static DatabaseManager *_sharedInstance;
if(!_sharedInstance) {
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_sharedInstance = [[super allocWithZone:nil] init];
});
}
return _sharedInstance;
}
+ (id)allocWithZone:(NSZone *)zone {
return [self sharedInstance];
}
- (id)copyWithZone:(NSZone *)zone {
return self;
}
- (id)init
{
self = [super init];
if (self != nil)
{
// Custom initialization
_someDictionary = [[NSMutableDictionary alloc] init];
}
return self;
}
Now, a VERY important thing is that, any place you want to use this object should first include the header:
EDIT: To use it in your code:
1) add the header
#import "DatabaseManager.h"
2) initialize the object
DatabaseManager *databaseManager = [DatabaseManager sharedInstance];
3) do whatever you need
// Initialize the dictionary
databaseManager.someDictionary = [[NSMutableDictionary alloc] initWithObjectsAndKeys:#"OBJECT",#"someKey", nil]; // In this case the object is just a NSString.
// Access
[databaseManager.someDictionary objectForKey:#"someKey"];
Put as a property on Appdelegate
#property (nonatomic,strong) NSDictionary * sharedData;
Access anywhere like
NSDictionary *sharedData= ((APPDelegate *) [UIApplication sharedApplication].delegate).sharedData;
I am trying to run a non-void function returning an NSArray, but when I run it, there's not even a log line:
- (NSArray *) arrayFunction
{
return myList;
}
This is how I call the function:
- (void) myMainFunction
{
[self arrayFunction];
}
I also tried with NSLog and a void function instead of NSArray, but that won't show up either.
It is a NSView class.
Thanks for you help!
*EDIT: * Full Code:
Implementation file:
#import "LogNavigator.h"
#implementation LogNavigator
- (id)initWithFrame:(NSRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code here.
}
[self myMainFunction];
return self;
}
- (void)drawRect:(NSRect)dirtyRect
{
// Drawing code here.
}
- (NSArray *) arrayFunction
{
// # Get the list of .txt files, this part works correctly as expected in CodeRunner
NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:#"Desktop"];
NSArray *directoryList = [[[NSFileManager defaultManager] contentsOfDirectoryAtPath:path error:nil]
pathsMatchingExtensions:[NSArray arrayWithObjects:#"txt", nil]];
return directoryList;
}
- (void) myMainFunction
{
[self arrayFunction];
}
#end
If this custom NSView is created using Interface Builder then you should override awakeFromNib:
- (void)awakeFromNib {
[self myMainFunction];
}
Note, however, that you are ignoring the return from arrayFunction, so it's feasible the compiler might omit the call entirely during an optmimized release build if it can determine no side effects of the call.
EDIT: Note that you need to set the NSView-derived class within the view of the window within MainMenu.xib, using IB, in order for this method to be triggered when the view is loaded.
When objects are loaded from a nib (or a Storyboard) The normal initialiser is not called, instead initWithCoder is called.
When setting up objects from a nib, you should override initWithCoder and put your initialiser code in there instead.
If you need to access or set up other objects in the nib as part of initialisation, then awakeFromNib is a better method to override, because it is called after all the other nib objects have been loaded.
edit
When you added the view object to the nib, did you specify it's class as LogNavigator? This is something that people frequently forget to do.
I have the following situation, i can't resolve:
#interface Deck : NSObject
#interface MasterDeck : Deck
#interface PlayerDeck : Deck
Inside MasterDeck class, as part of initialization, i call
[self cutDeckImageIntoCards]; // We don't get to execute this method
Call results in an error [PlayerDeck cutDeckImageIntoCards]: unrecognized selector sent to instance
Indeed, PlayerDeck does not have this method .. but why is it being called at all?
After looking at MasterDeck's initialization i added a few debugging statements:
static MasterDeck *gInstance = NULL;
+(MasterDeck *) instance {
#synchronized(self) {
if (gInstance == NULL) {
gInstance = [[self alloc] init];
}
}
return gInstance;
}
-(id) init {
if (gInstance != NULL) {
return gInstance;
}
// MasterDeck
self = [super init];
// PlayerDeck
if (self) {
// Lots of stuff
[self cutDeckImageIntoCards]
// Some more stuff
}
gInstance = self;
return gInstance;
}
Ok, so MasterDeck is PlayerDeck because' Deck thinks it is a PlayerDeck ... Deck confirms
Deck is created as follows:
static Deck *gInstance = NULL;
+(Deck *) instance {
#synchronized(self) {
if (gInstance == NULL) {
gInstance = [[self alloc] init];
}
}
return gInstance;
}
-(id) init {
if (gInstance != NULL) {
return gInstance;
}
self = [super init];
if (self) {
// Do something
}
NSLog(#"Deck thinks it's a %#", [[self class ]description]); // PlayerDeck
gInstance = self;
return gInstance;
}
So, again
#interface Deck : NSObject
Assuming above Singleton Implementation, why would Deck think it's actually a PlayerDeck?
So the way you've written this, if you create the PlayDeck instance first, then the Deck instance is now a PlayDeck.
And then if you go to create the MasterDeck instance, your call to [super init] dutifully returns that previous PlayDeck instance.
So why is Deck a singleton at all? Deck has two subclasses that are singletons, but are you really looking for a singleton Deck also?
At a minimum, you can make this sort of work by not setting gInstance from within each init. Let the class method do that. Just return self from each of the init's. Also, remove the check for gInstance being not null, other Deck's init will always return Deck's instance once you have an instance of Deck.
But beyond that, I would rethink this idea a bit. Hope that helps.
You'll probably want to separate your singleton class from the actual class.
Try implementing it as in this example,
+(id) instance {
static dispatch_once_t pred;
static MasterDeck *sharedInstance = nil;
dispatch_once(&pred, ^{
sharedInstance = [[MasterDeck alloc] init];
});
return sharedInstance;
}
What happens if you replace [[self alloc] init] with [[MasterDeck alloc] init]?
It may be that somehow self is PlayerDeck. To make sure, you could NSLog([self description]) just before calling + alloc.
Edit
I assume that the interesting part of the code you have above is part of the #implementation of MasterDeck. My suggestion would be to try a lot more logging, including determining what super and [self class] are before calling [super init], although these may be misleading...
Also, as a side note, I believe that you should call [self release] in init if you are returning the previously-created instance.
What does the [super init] method look like? Can you step into it, or is it the default initializer?
Edit 2
I think you're doing singletons wrong. If you initialize a PlayerDeck, that would create a singleton in Deck which is an instance of PlayerDeck. Then later, when you initialize a MasterDeck, calling [super init] will return the instance already created by the PlayerDeck.
It looks like you try to be clever, but fact is - often the computer is even smarter. :)
Your deck class caches an instance in gInstance - in fact, it looks like it may store a Deck, a PlayerDeck, or a MasterDeck, depending on what and how you call / instantiate first. After that, this very instance is returned by that init method.
I strongly suggest to get this code clean and readable. I bet there are numerous problems with this code - but your problem is already a good example. Your logic (which should be simple, I guess) can surely be implemented much easier.
Note - I'm not against singletons, but this sort of code stacking is an absolute no-go. It's hard to get more dependency logic into those lines. ;)
I'm trying to write my little app and experiencing some memory management problems.
At first, I have Game singleton object with property:
//Game.h
#interface Game : NSObject
#property (nonatomic, retain) MapBuildingsLayer *mapBuildingsLayer;
+(Game *) game;
-(BOOL) addObject:(NSString *) objName At:(CGPoint) pt;
#end
where MapBuildingsLayer is just cocos2d CCLayer instance
//Game.m
#implementation Game
#synthesize mapBuildingsLayer = _mapBuildingsLayer;
static Game *instance = nil;
+ (Game *)game {
#synchronized(self) {
if (instance == nil) {
instance = [[Game alloc] init];
}
}
return instance;
}
-(BOOL) addObject:(NSString *)objName At:(CGPoint)pt
{
if([objName isEqualToString:OBJ_TYPE_PIT])
{
if([[Game game].mapBuildingsLayer addPitAt:pt]) //app crashes here
{
[self toggleConstructionMode];
return YES;
}
}
return NO;
}
#end
In MapBuildingsLayer.m's init method I use Game's mapBuildingsLayer property to store a reference to this CCLayer instance in my singleton (for future use in other methods):
//MapBuildingsLayer.m
#implementation MapBuildingsLayer
-(id) init
{
if( (self=[super init])) {
[Game game].mapBuildingsLayer = self;
}
return self;
}
When I call Game's addObject:objName At: method, my app crashes with EXC_BAD_ACCESS.
How I must declare property in Game singleton to use it from other places in my app's lifetime?
You typically don't use the singleton in the class itself, try changing
if([[Game game].mapBuildingsLayer addPitAt:pt]) //app crashes here
to
if([self.mapBuildingsLayer addPitAt:pt]) //app crashes here
You should be using [Game game] external to the class to get into the singleton instance of your class and call its methods, but internal to the class you would just refer to it as self like normal.
Typically if you're going to use a game singleton this isn't how you'd use it. Try thinking of it like this with a giant state machine, Create a CCScene subclass which will initialize all of your respective CCLayer subclasses and control them. Then from the statemachine you can load the appropriate initializing its scene and that will create everything under it.
In your applicationDidFinishLaunching method you simply have your singleton object load your first scene. I'd really recommend checking out the Learning Cocos2d Book as it covers this singleton state engine very well and I think would clear up all your questions.
Bottom line is have the state engine load the scene which loads the layers.
No where in your code i am seeing your mapBuildingsLayer initialized. I hope before returning your instance you should also do
instance.mapBuildingsLayer = [CCLayer alloc] init];
I think the way you are assigning the mapBuildingsLayer is wrong. Remove [Game game].mapBuildingsLayer = self from your MapBuildingsLayer init method and instead add the following inside Game init method:
self.mapBuildingsLayer = [[MapBuildingsLayer alloc] init] autorelease];
now it is initialized inside your singleton init method so you can access it simply as [Game game].mapBuildingsLayer anywhere outside the Game class. If this doesnt work try posting what addPitAt: does.
hope this helps
I want to use a queue data structure in my Objective-C program. In C++ I'd use the STL queue. What is the equivalent data structure in Objective-C? How do I push/pop items?
Ben's version is a stack instead of a queue, so i tweaked it a bit:
NSMutableArray+QueueAdditions.h
#interface NSMutableArray (QueueAdditions)
- (id) dequeue;
- (void) enqueue:(id)obj;
#end
NSMutableArray+QueueAdditions.m
#implementation NSMutableArray (QueueAdditions)
// Queues are first-in-first-out, so we remove objects from the head
- (id) dequeue {
// if ([self count] == 0) return nil; // to avoid raising exception (Quinn)
id headObject = [self objectAtIndex:0];
if (headObject != nil) {
[[headObject retain] autorelease]; // so it isn't dealloc'ed on remove
[self removeObjectAtIndex:0];
}
return headObject;
}
// Add to the tail of the queue (no one likes it when people cut in line!)
- (void) enqueue:(id)anObject {
[self addObject:anObject];
//this method automatically adds to the end of the array
}
#end
Just import the .h file wherever you want to use your new methods, and call them like you would any other NSMutableArray methods.
I wouldn't say that using NSMutableArray is necessarily the best solution, particularly if you're adding methods with categories, due to the fragility they can cause if method names collide. For a quick-n-dirty queue, I'd use the methods to add and remove at the end of a mutable array. However, if you plan to reuse the queue, or if you want your code to be more readable and self-evident, a dedicated queue class is probably what you want.
Cocoa doesn't have one built in, but there are other options, and you don't have to write one from scratch either. For a true queue that only adds and removes from the ends, a circular buffer array is an extremely fast implementation. Check out CHDataStructures.framework, a library/framework in Objective-C that I've been working on. It has a variety of implementations of queues, as well as stacks, deques, sorted sets, etc. For your purposes, CHCircularBufferQueue is significantly faster (i.e. provable with benchmarks) and more readable (admittedly subjective) than using an NSMutableArray.
One big advantage of using a native Objective-C class instead of a C++ STL class is that it integrates seamlessly with Cocoa code, and works much better with encode/decode (serialization). It also works perfectly with garbage collection and fast enumeration (both present in 10.5+, but only the latter on iPhone) and you don't have to worry about what is an Objective-C object and what is a C++ object.
Lastly, although NSMutableArray is better than a standard C array when adding and removing from either end, it's also not the fastest solution for a queue. For most applications it is satisfactory, but if you need speed, a circular buffer (or in some cases a linked list optimized to keep cache lines hot) can easily trounce an NSMutableArray.
As far as I know, Objective-C does not provide a Queue data structure. Your best bet is to create an NSMutableArray, and then use [array lastObject], [array removeLastObject] to fetch the item, and [array insertObject:o atIndex:0]...
If you're doing this a lot, you might want to create an Objective-C category to extend the functionality of the NSMutableArray class. Categories allow you to dynamically add functions to existing classes (even the ones you don't have the source for) - you could make a queue one like this:
(NOTE: This code is actually for a stack, not a queue. See comments below)
#interface NSMutableArray (QueueAdditions)
- (id)pop;
- (void)push:(id)obj;
#end
#implementation NSMutableArray (QueueAdditions)
- (id)pop
{
// nil if [self count] == 0
id lastObject = [[[self lastObject] retain] autorelease];
if (lastObject)
[self removeLastObject];
return lastObject;
}
- (void)push:(id)obj
{
[self addObject: obj];
}
#end
There's no real queue collections class, but NSMutableArray can be used for effectively the same thing. You can define a category to add pop/push methods as a convenience if you want.
Yes, use NSMutableArray. NSMutableArray is actually implemented as 2-3 tree; you typically need not concern yourself with the performance characteristics of adding or removing objects from NSMutableArray at arbitrary indices.
re:Wolfcow -- Here is a corrected implementation of Wolfcow's dequeue method
- (id)dequeue {
if ([self count] == 0) {
return nil;
}
id queueObject = [[[self objectAtIndex:0] retain] autorelease];
[self removeObjectAtIndex:0];
return queueObject;
}
The solutions that use a category on NSMutableArray are not true queues, because NSMutableArray exposes operations that are a superset of queues. For example, you should not be allowed to remove an item from the middle of a queue (as those category solutions still let you do). It is best to encapsulate functionality, a major principle of object oriented design.
StdQueue.h
#import <Foundation/Foundation.h>
#interface StdQueue : NSObject
#property(nonatomic, readonly) BOOL empty;
#property(nonatomic, readonly) NSUInteger size;
#property(nonatomic, readonly) id front;
#property(nonatomic, readonly) id back;
- (void)enqueue:(id)object;
- (id)dequeue;
#end
StdQueue.m
#import "StdQueue.h"
#interface StdQueue ()
#property(nonatomic, strong) NSMutableArray* storage;
#end
#implementation StdQueue
#pragma mark NSObject
- (id)init
{
if (self = [super init]) {
_storage = [NSMutableArray array];
}
return self;
}
#pragma mark StdQueue
- (BOOL)empty
{
return self.storage.count == 0;
}
- (NSUInteger)size
{
return self.storage.count;
}
- (id)front
{
return self.storage.firstObject;
}
- (id)back
{
return self.storage.lastObject;
}
- (void)enqueue:(id)object
{
[self.storage addObject:object];
}
- (id)dequeue
{
id firstObject = nil;
if (!self.empty) {
firstObject = self.storage.firstObject;
[self.storage removeObjectAtIndex:0];
}
return firstObject;
}
#end
this is my implementation, hope it helps.
Is kind of minimalistic, so you must keep the track of the head by saving the new head at pop and discarding the old head
#interface Queue : NSObject {
id _data;
Queue *tail;
}
-(id) initWithData:(id) data;
-(id) getData;
-(Queue*) pop;
-(void) push:(id) data;
#end
#import "Queue.h"
#implementation Queue
-(id) initWithData:(id) data {
if (self=[super init]) {
_data = data;
[_data retain];
}
return self;
}
-(id) getData {
return _data;
}
-(Queue*) pop {
return tail;
}
-(void) push:(id) data{
if (tail) {
[tail push:data];
} else {
tail = [[Queue alloc]initWithData:data];
}
}
-(void) dealloc {
if (_data) {
[_data release];
}
[super release];
}
#end
Is there some particular reason you cannot just use the STL queue? Objective C++ is a superset of C++ (just use .mm as the extension instead of .m to use Objective C++ instead of Objective C). Then you can use the STL or any other C++ code.
One issue of using the STL queue/vector/list etc with Objective C objects is that they do not typically support retain/release/autorelease memory management. This is easily worked around with a C++ Smart Pointer container class which retains its Objective C object when constructed and releases it when destroyed. Depending on what you are putting in the STL queue this is often not necessary.
Use NSMutableArray.