I am watching a somewhat cruel behaviour momentarily: I have a ViewController for building a View programmatically. For this purpose I have stored the names of the UILabels that will be displayed in a NSDictionary that is held in an external class which is a singleton.
Unfortunately the NSDictionary is not accessible if I want to use the values in loadView. So I made some tests: The NSDictionary and its contents are availbale in init and the class is, of course, NSCFDictionary. If I have a look at it in loadView the class sometimes is NSCFDictionary and sometimes also CALayer or NSString?! I absolutely don't know what is happening??? This is the code I use:
- (id) init
{
self = [super initWithNibName:nil bundle:nil];
if (self)
{
UITabBarItem *tbi = [self tabBarItem];
[tbi setTitle:#"xxx"];
}
NSEnumerator *num = [[[ValueDispatcher dispatcher] labelDic] keyEnumerator];
NSLog(#"Class(init): %#", [[[ValueDispatcher dispatcher] labelDic] class]);
NSLog(#"No: %i", [[[ValueDispatcher dispatcher] labelDic] count]);
for (id key in num)
{
NSLog(#"Key %# Value %#", key, [[[ValueDispatcher dispatcher] labelDic] valueForKey:key]);
}
return self;
}
- (void)loadView
{
NSLog(#"Class(loadview)1: %#", [[[ValueDispatcher dispatcher] labelDic] class]);
NSLog(#"No: %i", [[[ValueDispatcher dispatcher] labelDic] count]);
NSEnumerator *num = [[[ValueDispatcher dispatcher] labelDic] keyEnumerator];
for (id key in num)
{
NSLog(#"Key34 %# Value %#", key, [[[ValueDispatcher dispatcher] labelDic] valueForKey:key]);
}
...
At which point between init and loadView can or will a NSDictionary be changed?
Btw, another info that might be important: If I use the above code and the NSDictionary is filled by an external service everything works fine. But if I fill the NSDictionary from a stored plist during startup it fails and I watch the described behaviour...
If I have a look at it in loadView the class sometimes is NSCFDictionary and sometimes also CALayer or NSString?
this (typically) means you have a reference count issue or you have not unregistered your observers correctly -- assuming you never set the dictionary. run instruments with zombies enabled.
At which point between init and loadView can or will a NSDictionary be changed?
a lot can happen in that time beyond the code you posted.
You'll need to retain that dictionary for as long your singleton needs it.
If you're using ARC, just make sure that ivar and/ or property are strong.
If you aren't using ARC, and you have a property setter to manage this for you, make sure you are actually using that setter.
And if no ARC, and you're setting your ivar directly, just make sure to retain the dictionary (and release the old one, if any)
Related
I find it hard to write/read array of custom objects. In my my app, Contact class has a NSDictionary as property and this dictionary has array as objects for keys.
I serialize/deserialize my objects with NSCoder and NSKeyedArchiever and even tried NSPropertyList serialization. I always get errors when serializing as soon as it starts to serialize NSDictionary. Here is my code and I didn't really find a general answer regarding how to serialize custom objects with complex structure?
//Contact.m
//phoneNumbers is a NSDictionary
#pragma mark Encoding/Decoding
-(void)encodeWithCoder:(NSCoder *)aCoder
{
NSLog(#"Encoding");
[aCoder encodeObject:self.firstName forKey:#"firstName"];
NSLog(#"First name encoded");
[aCoder encodeObject:self.lastName forKey:#"lastName"];
NSLog(#"Last name encoded");
[aCoder encodeInt:self.age forKey:#"age"];
NSLog(#"Age encoded");
NSString *errorStr;
NSData *dataRep = [NSPropertyListSerialization dataFromPropertyList:self.phoneNumbers
format:NSPropertyListXMLFormat_v1_0
errorDescription:&errorStr];
NSLog(#"Data class %#", [dataRep class]);
if(!dataRep)
{
NSLog(#"Error encoding %#", errorStr);
}
[aCoder encodeObject:dataRep forKey:#"phones"];
NSLog(#"Encoding finished");
}
- (id) initWithCoder: (NSCoder *)coder
{
if (self = [super init])
{
[self setFirstName:[coder decodeObjectForKey:#"firstName"]];
[self setLastName:[coder decodeObjectForKey:#"lastName"]];
[self setAge:[coder decodeIntForKey:#"age"]];
NSString *errorStr;
NSData *data=[coder decodeObjectForKey:#"phones"];
NSDictionary *propertyList = [NSPropertyListSerialization propertyListFromData:data mutabilityOption:NSPropertyListImmutable format:NULL errorDescription:&errorStr];
if(!propertyList)
{
NSLog(#"Error %#", errorStr);
}
[self setPhoneNumbers:propertyList];
}
return self;
}
//Serializing/Deserializing an array of Contact objects:
#pragma mark Import/Export
//Export Contacts to file
-(void)exportContactsToFile
{
BOOL done=[NSKeyedArchiver archiveRootObject:self.contacts toFile:[PathUtility getFilePath:#"phonebook"]];
NSLog(#"Export done: %i", done);
}
//Import Contacts from file
-(void)importContactsFromFile
{
self.contacts = [NSKeyedUnarchiver unarchiveObjectWithFile:[PathUtility getFilePath:#"phonebook"]];
}
Is there a generic good way to serialize/deserialize objects in objective-c? thanks
The error I get is:
0objc_msgSend
1 CF_Retain
...
that's stack trace, but I get no other errors(
You shouldn't need to use NSPropertyListSerialization for self.phoneNumbers. NSDictionary adheres to the NSCoding protocol.
So, [aCoder encodeObject:self.phoneNumbers forKey:#"phones"]; should be sufficient.
As long as a class adheres to NSCoding (which nearly all Apple-provided class do), you can just use -encodeObject:forKey:, since that method will call that object's implementation of -encodeWithCoder:
I have a special class in my proprietary library that automatically reads the list of its properties and use the getter and setter to encode and decode the object. Sorry I can't share the code here but I can at least give you steps by steps how my class works:
First, the class must be implement NSCoding and NSCopying protocols.
Inside + (void)initialize, iterate thru the definitions of the properties of the class using class_copyPropertyList(), property_getName() and property_copyAttributeList(). Refer Objective-C Runtime Programming Guide for details on these functions.
For each property, run thru its attribute list and get the attribute with strncmp(attribute.name, "T", 1) == 0 (yup, it's a c-string in there). Use that attribute value to determine the type of the property. For example, "i" means int, "I" means unsigned int, if it starts with a "{" then it's a struct etc. Refer this page on the Type Encoding.
Store the property name-type pairs inside a NSDictionary. At the end of properties iteration, store this dictionary inside a static and global NSMutableDictionary using the class name as the key.
To support auto-encoding, implement - (void)encodeWithCoder:(NSCoder *)aCoder to iterate thru the property name-type pair, calling the property getter method (usually - (returnType)propertyName) and encode it inside the coder using appropriate encodeType: method (e.g. encodeInt:, encodeFloat:, encodeObject:, encodeCGPoint: etc).
To support auto-decoding, implement - (id)initWithCoder:(NSCoder *)aDecoder to iterate thru the property name-type pair, decode it from the decoder using appropriate decodeTypeForKey: method (e.g. decodeIntForKey:, decodeFloatForKey:, decodeObjectForKey:, decodeCGPointForKey: etc). and call the property setter method (usually - (void)setPropertyName:).
Implement an instance method that trigger the encoding (luckily I can share this method here ^__^):
NSMutableData *data = [NSMutableData data];
NSKeyedArchiver *arc = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[arc encodeRootObject:self];
[arc finishEncoding];
[arc release];
return data;
Once you have the NSData you can anything with it such as calling writeToFile:atomically: or even [[NSUserDefaults standardUserDefaults] setObject:[self wrapInNSData] forKey:key].
Also, implement a class method that returns a new instance of the object loaded from the file:
NSKeyedUnarchiver *unarc = [[NSKeyedUnarchiver alloc] initForReadingWithData:[NSData dataWithContentsOfFile:dataFilePath]];
MyCoolFileDataStore *data = [unarc decodeObject];
[unarc release];
return data;
Finally, to make another object class supports this auto-encoding-decoding, the class needs to extend the special class.
Sorry, it's a bit long winded, but for my case, the extra trouble that I took to create this class really save a lot of time along the road. Struggle today, breeze through tomorrow ;)
I've created a subclass of UIImage (UIImageExtra) as I want to include extra properties and methods.
I have an array that contains instances of this custom class.However when I save the array, it appears the extra data in the UIImageExtra class is not saved.
UIImageExtra conforms to NSCoding, but neither initWithCoder or encodeWithCoder are called, as NSLog statements I've added aren't printed.
My method to save the array looks like this:
- (void)saveIllustrations {
if (_illustrations == nil) {
NSLog(#"Nil array");
return;
}
[self createDataPath];
//Serialize the data and write to disk
NSString *illustrationsArrayPath = [_docPath stringByAppendingPathComponent:kIllustrationsFile];
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:_illustrations forKey:kIllustrationDataKey];
[archiver finishEncoding];
[data writeToFile:illustrationsArrayPath atomically: YES];
}
And the UIImageExtra has the following delegate methods for saving:
#pragma mark - NSCoding
- (void)encodeWithCoder:(NSCoder *)aCoder {
NSLog(#"Encoding origin data!");
[super encodeWithCoder:aCoder];
[aCoder encodeObject:originData forKey:kOriginData];
}
- (id)initWithCoder:(NSCoder *)aDecoder {
if (self = [super initWithCoder:(NSCoder *) aDecoder]) {
NSLog(#"Decoding origin data");
self.originData = [aDecoder decodeObjectForKey:kOriginData];
}
return self;
}
My code to create the array in the first place looks like this (in case that offers any clues)
for (NSDictionary *illustrationDict in illustrationDicts) {
NSString *illustrationString = [illustrationDict objectForKey:#"Filename"];
NSNumber *xCoord = [illustrationDict objectForKey:#"xCoord"];
NSNumber *yCoord = [illustrationDict objectForKey:#"yCoord"];
UIImageExtra *illustration = (UIImageExtra *)[UIImage imageNamed:illustrationString];
//Scale the illustration to size it for different devices
UIImageExtra *scaledIllustration = [illustration adjustForResolution];
NSValue *originData = [NSValue valueWithCGPoint:CGPointMake([xCoord intValue], [yCoord intValue])];
[scaledIllustration setOriginData:originData];
[self.illustrations addObject:scaledIllustration];
}
Or am I just going about saving this data the wrong way? Many thanks.
Your code to initialize the array is not actually creating instances of your UIImageExtra subclass.
UIImageExtra *illustration = (UIImageExtra *)[UIImage imageNamed:illustrationString];
returns a UIImage. Casting it doesn't do what you were intending.
UIImageExtra *scaledIllustration = [illustration adjustForResolution];
is still just a UIImage.
One straightforward-but-verbose way to approach this would be to make UIImageExtra a wrapper around UIImage. The wrapper would have a class method for initializing from a UIImage:
+ (UIImageExtra)imageExtraWithUIImage:(UIImage *)image;
And then every UIImage method you want to call would have to forward to the wrapped UIImage instance-- also being careful to re-wrap the result of e.g. -adjustForResolution lest you again end up with an unwrapped UIImage instance.
A more Objective-C sophisticated approach would be to add the functionality you want in a Category on UIImage, and then use method swizzling to replace the NSCoding methods with your category implementations. The tricky part of this (apart from the required Objective-C runtime gymnastics) is where to store your "extra" data, since you can't add instance variables in a category. [The standard answer is to have a look-aside dictionary keyed by some suitable representation of the UIImage instance (like an NSValue containing its pointer value), but as you can imagine the bookkeeping can get complicated fast.]
Stepping back for a moment, my advice to a new Cocoa programmer would be: "Think of a simpler way. If what you are trying to do is this complicated, try something else." For example, write a simple ImageValue class that has an -image method and an -extraInfo method (and implements NSCoding, etc.), and store instances of that in your array.
You can't add objects to an NSArray after init. Use NSMutableArray, that might be the issue.
Hi im trying to retrieve an object of a specific class from an NSMutableArray, and then add it to self: eg:
- (void) init{
_Objects = [[NSMutableArray alloc]init];
Psychicing *psy = [[Psychicing alloc]init];
[psy startPsychic];
[_Objects addObject: psy];
[psy release];
}
This creates an object of class Psychicing, then runs the [psy startPsychic] method to create the internals of the class object. Then I add the psy object to _Objects NSMutableArray.
-(void)startPsychic{
id psychicParticle = [CCParticleSystemQuad ......]; //is Synthesised with (assign)
//Other things are set here such as position, gravity, speed etc...
}
When a touch is detected on screen, I want to take the psy object from the _Objects array and add it to self: Something like this (Although this gives runtime error)
-(void) Touches.....{
for (Psychicing *psy in _Objects){
[self addChild: psy.psychicParticle];
}
}
I hope i have explained it clearly enough, if you need more clarification let me know.
So basically:
[MainClass Init] -> [Psychicing startPsychic] -> [MainClass add to array] -> [MainClass add to self]
I'm assuming the _Objects (which should be a lowercase o to follow conventions) is storing objects other than the Psychicing object and you're trying to pull just the Psychicing object out of it in the -(void)Touches... method (which also should be lowercase). If so, you could do:
for (id obj in _Objects)
{
if ([obj isMemberOfClass:[Psychicing class]])
[self addChild:obj.psychicParticle];
}
That will cause only the Psychicing objects in the array to be added as a child to self.
It looks like you do have another error though if the code you pasted in is your real code. Init should be defined as:
- (void) init{
_Objects = [[NSMutableArray alloc]init];
Psychicing *psy = [[Psychicing alloc]init];
[psy startPsychic];
[_Objects addObject: psy];
[psy release];
}
with _Objects defined as an instance variable (or property) in the class's interface. As you wrote it, it's a method variable in the init method and is leaking. So when you try to access _Objects in -touches, _Objects is most likely nil.
Okay, with the help of McCygnus I got it working, the only thing missing with a pointer to the id object:
for (id obj in _Objects){
if ([obj isMemberOfClass:[Psychicing class]]){
Psychicing *apsy = obj;
[apsy.psychicParticle setPosition:location];
[self addChild:apsy.psychicParticle];
}
}
Please look at the code below and suggest the best approach. I can't quite tell whether the code is correct. When adding objects to arrays, do they get a retain count? In the second function, am I releasing the local variable "mySubview" or the original object?
// this is a class property
myArray = [[NSMutableArray alloc] init];
- (void)createSubview
{
UIView *mySubview = [[UIView alloc] init];
[self addSubview:mySubview];
[myArray addObject:mySubview];
}
-(void)eventHandler:(NSNotification *) notification
{
UIView *mySubview = [notification object];
[myArray removeObjectIdenticalTo:mySubview];
[mySubview removeFromSuperview];
[mySubview release];
}
When adding objects to arrays, do they
get a retain count?
Yes.
In the second function, am I releasing
the local variable "mySubview" or the
original object?
UIView *mySubview;' defines a local variable, mySubview, which is a pointer to -- a reference to -- an instance of the UIView class. There is no such thing as a "local object" or "stack object" in Objective-C (save for blocks, but that is beyond the scope of this question).
So, no, when you call [mySubview release] you are sending -release to the instance of of UIView included in notification.
That release is balancing the retain implied by the alloc. Which isn't the right pattern at all. You should do something like:
- (void)createSubview
{
UIView *mySubview = [[UIView alloc] init];
[self addSubview:mySubview];
[myArray addObject:mySubview];
[mySubview release];
}
-(void)eventHandler:(NSNotification *) notification
{
UIView *mySubview = [notification object];
[myArray removeObjectIdenticalTo:mySubview];
[mySubview removeFromSuperview];
}
Oh, by "class property", I'm assuming you mean "instance variable"?
I have a weird problems with NSArray where some of the members of the objects in my array are going out of scope but not the others:
I have a simple object called Section.
It has 3 members.
#interface Section : NSObject {
NSNumber *section_Id;
NSNumber *routeId;
NSString *startLocationName;
}
#property(nonatomic,retain) NSNumber *section_Id;
#property(nonatomic,retain) NSNumber *routeId;
#property(nonatomic,retain) NSString *startLocationName;
#end
#implementation Section
#synthesize section_Id;
#synthesize routeId;
#synthesize startLocationName;
//Some static finder methods to get list of Sections from the db
+ (NSMutableArray *) findAllSections:{
- (void)dealloc {
[section_Id release];
[routeId release];
[startLocationName release];
[super dealloc];
}
#end
I fill it from a database in a method called findAllSection
self.sections = [Section findAllSections];
In find all sections I create some local variables fill them with data from db.
NSNumber *secId = [NSNumber numberWithInt:id_section];
NSNumber *rteId = [NSNumber numberWithInt:id_route];
NSString *startName = #"";
Then create a new Section and store these local variable's data in the Section
Section *section = [[Section alloc] init];
section.section_Id = secId;
section.routeId = rteId;
section.startLocationName = startName;
Then I add the section to the array
[sectionsArray addObject:section];
Then I clean up, releasing local variables and the section I added to the array
[secId release];
[rteId release];
[startName release];
[locEnd_name release];
[section release];
In a loop repeat for all Sections (release local variables and section is done in every loop)
The method returns and I check the array and all the Sections are there. I cant seem to dig further down to see the values of the Section objects in the array (is this possible)
Later I try and retrieve one of the Sections
I get it from the array
Section * section = [self.sections objectAtIndex:row];
Then check the value
NSLog(#" SECTION SELECTED:%#",section.section_Id);
But the call to section.section_Id crashed as section.section_Id is out of scope.
I check the other members of this Section object and they're ok.
After some trial and error I find that by commenting out the release of the member variable the object is OK.
//[secId release];
[rteId release];
[startName release];
[locEnd_name release];
[section release];
My questions are:
Am I cleaning up okay?
Should I release the object added to an array and the local variable in the function?
Is my dealloc okay in Section?
Does this code look ok and should I be looking elsewhere for the problem?
I'm not doing anything complicated just filling array from DB use it in Table Cell.
I can comment out the release but would prefer to know why this works, and if I shouldn't be doing this. The only place that secId is released is in the dealloc.
You should not be releasing secId, rteId, or startName. secId and rteId are pointers to NSNumber instances created with a factory method that returns an already-autoreleased object. Static strings (i.e. #"") do not need to be released. You need to re-read the Memory Management Programming Guide. Then read it again ;-) It will be your friend.
You're releasing objects you don't own. You should read the memory management rules.
I'll second (third) the suggestion to read the memory management rules.
The TL;DR version is anything you alloc and call a method with init in the method name on is your responsibility to release. For instance:
NSString *string = [[NSString alloc] initWithFormat:#"%#", someObject];
In this case you must release string. However:
NSString *string = [NSString stringWithFormat:#"%#", someObject];
Here string is autoreleased. It's basically equivalent to this:
NSString *string = [[[NSString alloc] initWithFormat#"%#", someObject] autorelease];
...meaning that the next time through the event loop (which means possibly as soon as your function returns), the system will send a release message to it for you. Apple calls these "convenience methods".
If you have something like this:
NSString *string = #"foo";
Then string is pointing to an instance of NSString that is created by the runtime when your program initializes and won't go out of scope until your program terminates. Never release these either.
Again, read the guidelines and bookmark them. But this should answer your direct question.