I have a problem with the init() method of a standard NSObject. I wrote a class (EFAPersistence) which is a subclass of NSObject. EFAPersistance has a attribute called efaDatabase.
EFAPersistence.h
#interface EFAPersistence : NSObject {
FMDatabase * efaDatabase;
}
#property (assign) FMDatabase * efaDatabase;
Everytime an instance of EFAPersistance is created I want to assign efaDatabase a value from my AppDelegate.
EFAPersistence.m
#implementation EFAPersistence
#synthesize efaDatabase;
- (id)init {
if (self = [super init]) {
efaDatabase = [[NSApp delegate] efaDatabase];
}
return self;
}
#end
This way of assigning does not work. But it works if I put the code in a normal method. So I am sure that efaDatabase is correctly instantiated in my AppDelegate. It's just not working in my init() method. That's why I have the feeling that NSApp is not working inside the init() method.
That's how the important AppDelegate code looks like.
AppDelegate.h
#interface AppDelegate : NSObject <NSApplicationDelegate> {
FMDatabase * efaDatabase;
}
AppDelegate.m
- (id)init {
if (self = [super init]) {
NSString * databasePath =
[[NSBundle mainBundle] pathForResource:#"efa" ofType:#"sqlite"];
self.efaDatabase = [FMDatabase databaseWithPath:databasePath];
if (![efaDatabase open]) {
NSLog(#"Couldn't open database: %#", databasePath);
// TODO: Create a database here
}
self.db = [[EFAPersistence alloc] init];
}
return self;
}
As you can see I am calling the init method. I also affirmed this by using NSLog(). init() is called. The attribute I am trying to assign in EFAPersistence is also created before init() is called.
To sum everything up:
How can I make this work within the init() method so I do not have to write boiler plate code in all my methods of EFAPersistence?
It looks to me that your AppDelegate is unset when you try to create the EFAPersistance object the first time. This is on below line in AppDelegate.m
self.db = [[EFAPersistence alloc] init];
I imagine the app delegate is set after the init is done (returned).
This way of assigning does not work. But it works if I put the code in a normal method. So I am sure that efaDatabase is correctly instantiated in my AppDelegate. It's just not working in my init() method. That's why I have the feeling that NSApp is not working inside the init() method.
NSApp works fine.
Quoting epatel:
I imagine the app delegate is set after the init is done (returned).
Correct. The nib loader completely instantiates each object (including the app delegate, if it's in a nib), then sets it as the value of any properties it's connected to. These are two separate operations; it will not set a not-yet-initialized object as the application delegate.
Quoting you (Jens) again:
The question is how to assign efaDatabase in EFAPersistences only once . There are other methods like awakeFromNib and viewDidLoad etc. But those are not available in a plain NSObject subclass.
Incorrect. awakeFromNib is sent to every object in a nib after the object has been initialized.
That said, I'm curious as to why you have EFAPersistence in a nib. From its name, it doesn't sound interface-related. Shouldn't the app delegate own the EFAPersistence, and the EFAPersistence own the database directly?
Related
I am trying to initialise a variable in my init method, but it seems to get deallocated when the call chain reaches awakeFromNib. I've read several threads and far too many seem to share the same confusion - something that should be really simple and straightforward... :(.
- (id)init {
self = [super initWithNibName:#"MyViewController" bundle:[NSBundle mainBundle]];
if (self) {
self.customObject = [CustomObject currentInstance]; //OK
}
}
- (void)awakeFromNib {
[self.customObject someMethod]; //here self.customObject is nil?
//self.customObject = [CustomObject currentInstance]; // Why should I do this here?
}
Nothing fancy about the declarations, in my .m file there's. I don't want to assign the property in awakeFromNib without understanding the reason behind.
#property (strong) CustomObject *customObject;
CustomObject instantiation .m file
static CustomObject customObject;
#implementation CustomObject {
+ (instancetype)initMockCustomObject {
customObject = (CustomObject*)[OCMockObject mockForClass:[CustomObject class]];
}
+ (instancetype)currentInstance {
if ( customObject == nil) { [NSException raise...]; }
return customObject;
}
}
initMockCustomObject has already been called in AppDelegate.
Edit: added the actual super call to initWithNibName method in init.
Edit2: added the singleton instance
thank you for your input. I've created a sandbox project with the absolute minimum, and I found that I had an object in one of my parent NIBs, that was of the same type as MyViewController, causing this problem. Closing this question as it's too app specific. The fundamental question of initialising variables in init is OK.
I'm developing an app in Objective-C using ARC.
My simplified code looks like this:
ClassA (.m)
MyCustomClass *obj = [[MyCustomClass alloc] initWithValue1:#"abc" value2:1000];
MyViewController *vc = [[MyViewController alloc] initWithObject:obj];
// "vc" will become the first item of a UITabBarController
MyViewController (.h)
- (id)initWithObject:(MyCustomClass *)obj {
...
localReferenceToOjbect = obj;
...
}
- (void)viewWillAppear:(BOOL)animated {
// do something with "localRefernceToObject" <---
}
launching the app will result in a call to a zombie: when the ViewController is shown, the "obj" will be already deallocated and so i can't use it anymore.
my workaround is:
ClassA (.h)
#interface ClassA : UIViewController {
MyCustomClass *obj;
}
ClassA (.m)
obj = [[MyCustomClass alloc] initWithValue1:#"abc" value2:1000];
MyViewController *vc = [[MyViewController alloc] initWithObject:obj];
// "vc" will become the first item of a UITabBarController
is this the right way?! i don't think so: why i've to store an istance of an object that is useless for ClassA?
i can't get an explanation on what's actually happening. could you help me?
You're right in the fact that it is not logical to keep around a reference to obj in ClassA.
But if you need to keep around the reference to obj for MyViewController to use it, retain it in MyViewController, not in ClassA, because that's MyViewController that will use it.
The easiest way to do this is to transform your localReferenceToObject you use in MyViewController into a #property(retain) propertyToObject; (or #property(strong) propertyToObject if you use ARC) and access it in your MyViewController.m with self.propertyToObject (instead of localReferenceToObject, to be sure to call the property's setter and thus really retain the object).
This way, the object will be retained and kept around while your MyViewController instance is still alive.
[EDIT] If you want this property to be private, you can declare it in the class extension so that it is not accessible from other classes, as in the below example. See here in Apple's documentation for more details.
In your MyViewController.h header file
#interface MyViewController : UIViewController
// Here you write the public API in the .h / public header
// If you don't want your property to be visible, don't declare it there
#end
In your MyViewController.m file
#interface MyViewController ()
// This is the private API, only visible inside the MyViewController.m file and not from other classes
// Note the "()" to declare the class extension, as explained in Apple doc
#property(nonatomic, retain) MyCustomClass* referenceToObject; // Note: use strong (which is a synonym of retain) if you use ARC
#end
#implementation MyViewController
#synthesize referenceToObject = _referenceToObject; // not even needed with modern ObjC and latest LLVM compiler
- (id)initWithObject:(MyCustomClass *)obj
{
self = [super init];
if (self) {
...
self.referenceToOjbect = obj;
...
}
return self;
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// do something with "self.refernceToObject"
}
// This memory management code is only needed if you don't use ARC
-(void)dealloc
{
self.referenceToObject = nil; // release memory
[super dealloc];
}
Personally, as suggested by Apple in some WWDC sessions, I now really rarely use instance variables and prefer the use of properties instead, either public in the .h or private in the .m.
If you use ARC, you can still use an instance variable instead of a property as ARC will retain it for you, but as long as you make sure your instance variable is declared as strong and not weak.
I have been seeing some strange behavior when I try to access a class variable or a property in my drawRect method..
In my .h file I have the following
#interface DartBoard : UIView
{
Board * board;
int index;
}
#property (readwrite, assign, nonatomic) NSNumber * selectedIndex;
#end
In my .m file I have the following
#implementation DartBoard
#synthesize selectedIndex;
-(id)init
{
self.selectedIndex = [NSNumber numberWithInt:5];
index = 123;
return self;
}
- (void)drawRect:(CGRect)rect {
NSLog(#"selectedIndex: %d",[self.selectedIndex intValue]);
NSLog(#"index: %d",index);
}
#end
the output is
2012-06-12 19:48:42.579 App [3690:707] selectedIndex: 0
2012-06-12 19:48:42.580 App [3690:707] index: 0
I have been trying to find a solution but have had no luck..
I found a similar question but there was no real answer to the issue
See: UIView drawRect; class variables out of scope
I have a feeling drawRect is different that normal methods and is not getting the scope of the class correctly but how do I fix it?
Cheers
Damien
I have a feeling drawRect is different that normal methods and is not getting the scope of the class correctly
No, there is nothing special about -drawRect:.
There are two possibilities:
1. Your -init method is not being called.
You didn't say how this view gets created -- if you are manually calling [[DartBoard alloc] init], or if it is getting unarchived from a nib file.
If it's coming from a nib, UIView's unarchiving doesn't know that your init method should be called. It will call the designated initializer instead, which is -initWithFrame:.
So, you should implement that method instead, and make sure to call super!
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
self.selectedIndex = [NSNumber numberWithInt:5];
index = 123;
}
return self;
}
2. There might be two instances of your view: one that you are manually initing, and another one that comes from somewhere else, probably a nib. The second instance is the one that is being drawn. Since its variables and properties are never set, they show up as zero (the default value).
You could add this line to both your -init and -drawRect: methods, to see what the value of self is. (Or, check it using the debugger.)
NSLog(#"self is %p", self);
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 have some class initialized in Appdelegate, but when I get this class instance form Appdelegate in another class it has "fresh" state.
I have following in AppDelegate:
Interface:
#property (nonatomic, retain) DataController *dataController;
Implementation:
#synthesize dataController;
- (id)init {
if (self = [super init]) {
DataController *controller = [[DataController alloc] init];
self.dataController = controller;
[controller release];
NSLog(#"items: %d",[self.dataController numberOfItems]);
}
return self;
}
At this point DataControlelr class loads objects form database. Log output show "items: 10".
I have TableViewController where I need to use DataController.
TableViewController header:
#interface TableViewController : UITableViewController {
DataController *dataController;
}
#property (retain) DataController *dataController;
#end
Implementation:
-(id)init{
if (self =[super init]) {
DataController *dc =[(AppDelegate *)[[UIApplication sharedApplication] delegate] dataController];
[dc retain];
dataController = dc;
NSLog(#"items: %d",[self.dataController numberOfItems]);
}
return self;
}
Here it always says that DataController has 0 items. "fresh" state.
The Log output is always
items: 10
items: 0
It seems like assigning that class creates reference to freshly initialised DataController somehow?
How do I reference another class properly?
Thanks.
The first thing to check would be to ensure that the dc variable in the second class isn't nil-- that would cause any method called on it to 'return' 0.
It might also be useful to print out the address of the app delegate from both of those methods-- just in case the -init method is resulting from an incorrectly-allocated second instance of that class somewhere, while the regular version hasn't been initialized in the same way (or was using -initWithCoder:, etc.)
One useful rule of thumb for initialization of objects created or assigned within a nib file is to use -awakeFromNib to perform most of your initialization tasks. A corollary to this is that the app delegate can set up its state in response to the -applicationDidFinishLaunching: method. In this case, if there is a second instance of your AppDelegate class being allocated somewhere, only the one which is really set as the app's delegate will receive -applicationDidFinishLaunching:.
At the end of the day, stepping through in the debugger and looking at the call stack should show you if something isn't happening in quite the way it should.
Could there be an issue with your assignment of dataController = dc in TableViewController? In your log statement you use self.dataController, should your assignment directly above it be self.dataController = dc ?
I found the gotcha. Tanks to Jim!
Moved assignment from -init to -awakefromnib and now DataController is valid.
My mistake is that after putting the code initially in -viewDidLoad and -viewWillAppear which was wrong I thought that in -init is the place for the assignment.