I am trying to save an image in an NSMutable array and it is not working
here is what I am doing
[imagesList addObject:[UIImage imageNamed:#"b.png"]];
after executing this line I noticed that the number of objects remains 0
any reason ?
Thanks
I repeate this code in several areas :
Globally I declare :
NSMutableArray *imagesList;
NSUserDefaults *imagesHistory;
in my viewdidload method I write:
imagesHistory=[NSUserDefaults standardUserDefaults]; //imagesHistory is created globallt as NSUserDefault imagesHistory
[imagesHistory setObject:imagesList forKey:#"images history"];
UIImage *image;
image=[UIImage imageNamed:#"b.png"];
[imagesList addObject:image];
imagesHistory=[NSUserDefaults standardUserDefaults];
[imagesHistory setObject:imagesList forKey:#"images history"];
and in the didFinishLaunchingWithOptions I write : (even though I don t need to do it when I am adding strings ...)
imagesList = [[NSMutableArray alloc] init];
Regardless of whether it is a global variable or not, you still need to call alloc and init SOMEWHERE for the object. If you intend to use it throughout your app, then appDidFinishLaunchingWithOptions is a decent place to add this call:
imagesList = [[NSMutableArray alloc] init];
Is your empty array being retained? If you're not using Automatic Reference Counting, there's a good chance you're initializing the array with the following
imagesList = [[NSMutableArray alloc] init];
but it's not being retained. You'll want to retain the empty array so it gets appended to further on in your code.
imagesList = [[[NSMutableArray alloc] init] retain];
Just don't forget to release the array when you're all done with it, in viewDidUnload or wherever is appropriate.
You're allocating/initing imagesList AFTER you try to add an object. You need to alloc/init imageList before you add anything to it.
To make sure it's there, try something like this:
if (!imagelist) imageList = [[NSMutableArray alloc] init];
If it exists, and you're still having this problem, it's possible that you're allocating/initing a new NSMutableArray and assigning it to imageList after you've added the object. This means the old array would be discarded and you'd be left with a new array with zero items.
try UIImageView *image;
image=[UIImage imageNamed:#"b.png"];
also, in #property(nonatomic,retain) use 'strong' instead of 'retain'
Related
So, when I modify things inside of an NSMutableArray I don't get the result I expect. I think the best way to frame this question is with an example. The following code prints "george" (as expected):
NSMutableArray *originalArray = [[NSMutableArray alloc] initWithObjects:#"sally",#"george", nil];
NSMutableArray *secondArray = [[NSMutableArray alloc] init];
[secondArray addObject:originalArray[1]];
secondArray[0] = #"priscilla";
NSLog(#"%#",originalArray[1]);
But this code prints "priscilla":
TestClass *test1 = [[TestClass alloc] init];
test1.clientName = #"sally";
TestClass *test2 = [[TestClass alloc] init];
test2.clientName = #"george";
NSMutableArray *originalArray = [[NSMutableArray alloc] initWithObjects:test1,test2, nil];
NSMutableArray *secondArray = [[NSMutableArray alloc] init];
[secondArray addObject:originalArray[1]];
TestClass *objectTakenFromSecondArray = secondArray[0];
objectTakenFromSecondArray.clientName = #"priscilla";
NSLog(#"%#", ((TestClass *)originalArray[1]).clientName);
I thought that addObject: always copied the object before adding it to the array receiving the addObject: message. Is this not the case?
Thanks!
p.s. here is the interface and implementation for TestClass in case it is pertinent:
#interface TestClass : NSObject
#property (strong,nonatomic) NSString *clientName;
#end
#implementation TestClass
#synthesize clientName = _clientName
#end
I thought that addObject: always copied the object before adding it to the array receiving the addObject: message. Is this not the case?
addObject: does not copy the object. NSArray does not require that its contents even be copyable (not everything is). That probably explains the confusion. If you want to copy it, you need to do so yourself.
You pretty much answered your own question. When you create an NSMutableArray and add an object to it, you are just creating a pointer to that object, wherever it is stored. If you add the same object to another NSMutableArray, that too contains a pointer to the same thing. You might not need the analogy, but for anyone else confused - the NSMutableArray is like a postman with an address to post to, and the object is the house at that address. Two postmen (or two arrays) can have an address for the same house, but there is only one house still. (That is, unless someone explicitly 'copies' the house).
So in your second to last line of code, where you change that .clientName property, you are changing the property of the original *test2 object.
Worth noting in this case, that if you remove that second array, you don't remove the objects it contains necessarily. So in your case, removing that second NSMutableArray from memory does not mean that all of its objects also disappear from memory - unless everything else that points to those objects also is removed. The array does not contain pointers to unique copy of those objects - it just points to the originals.
So I have this method:
-(void)addLaneToRacingLanes:(UITapGestureRecognizer*)sender{
laneDataObject *data=[self.laneDataObjects objectAtIndex:sender.view.tag];
[self.racingLanes addObject:data];
NSLog(#"%i",self.racingLanes.count);
[sender.view setBackgroundColor:[UIColor yellowColor]];
}
It uses the tag from the senders view to find out which data object corresponds to that view.I'm using this to add to my racingLanes which is how I update these views, but my problem is that for some reason I cant add my laneDataObjects to my array racingLanes. Any ideas?
This is how the properties are set up:
#property (strong,nonatomic)NSArray *laneDataObjects;
#property (strong,nonatomic) NSMutableArray *racingLanes;
I have already run through the tags and they all work. The tags work such that lane 1 is tag 0 with its data object at 0, then lane 2 is tag 1 and its data is 1, so on and so forth. I already pre-tested this. And I have checked that both the laneDataObject array has been properly set up. Is it because my racingLanes isn't using a custom getter or setter? How would I go about changing that?
Incase it matters I used
NSLog(#" %i",self.racingLanes.count);
to find out if the array was empty.
It is a near certainty that the racingLanes has not been initialized: since the objects that you are adding are non-nil (you'd see an exception thrown otherwise) the racingLanes must be nil then.
You need to set racingLanes to NSMutableArray in the designated initializer:
_racingLanes = [NSMutableArray array];
Did you make sure to initialize your NSMutableArray in your class's -init or -viewDidLoad function?
// WITH ARC
self.racingLanes = [NSMutableArray array];
// WITHOUT ARC
self.racingLanes = [[NSMutableArray alloc] init];
Please help me i have a NSMutableArray which contains data until viewDidLoad is finished.
When I click any button I try to get the data in it and it just disappears.
If you created your array with a variant of [NSMutableArray array] it will be autoreleased. Assuming myArray is a property of your class, you should use
myArray = [[NSMutableArray] alloc] init]; //or initWithCapacity, etc.
If you still use reference counting, you need to add [myArray retain]; unless it is already retained in the #property declaration and release it in viewDidUnload:.
i have created a script, witch load the XML from server parse it an save it to NSMutableArray
[kategorienArray addObject:catName];
catName ist a String, if i NSLog the Array everything works fine.
After that i have created a tebleview, and reload Data
[kategorienAuswahl reloadData];
KategorienAuswahl is my TableView
and now a get the Problems
if i Use a "normal" array
NSArray *array = [[NSArray alloc] initWithObjects:#"iPhone", #"iPod", #"iPad",nil];
self.listData = array;
[array release];
the will be displayed, but if i use
cell.textLabel.text = [kategorienArray objectAtIndex:row];
i get EXC_BAD_ACCESS
instead it works fine with
cell.textLabel.text = [listData objectAtIndex:row];
I Add nwo
kategorienArray = [[NSMutableArray alloc] init];
kategorienArray = [NSMutableArray arrayWithCapacity:10];
but now i get no data in my Tableview
You might not have initialized your kategorienArray.
Do you have a kategorienArray = [[NSMutableArray alloc] init]; in your code? You should have done this before adding objects to it and then accessing them.
Also, make sure your array is retained at the point where it's created, so that the system doesn't reclaim its memory before you access its items. The way I use to make sure things are going right is to declare the mutable array as a property. In your viewcontroller's .h file put
#property (nonatomic, retain) NSMutableArray *kategorienArray;
and in your .m file put
#synthesize kategorienArray;
at the top and then
self.kategorienArray = [NSMutableArray array];
in viewDidLoad or somewhere, before adding items to it.
The problem may be that 'kategorienArray' has been (auto)released.
Is 'kategorienArray' an ivar ?
Check out if when you created the array you correctly retained it (particularly if you created it with a class method).
umm So simple question here:
I have an instance of NSMutableArray declared in my header
NSMutableArray *day19;
#property (nonatomic, retain) NSMutableArray *day19
implementation:
#synthesize day19;
In my viewDidLoad
self.day19 = [[NSMutableArray alloc] init];
In the myMethod where I want to add objects to the array I:
NSObject *newObject = [[NSObject alloc] init];
[day19 addObject:newObject];
However... when i check the day19 array there is nothing in it. If I conversely add the newObject to a tempArray within the myMethod scope and then set the day19 array to the tempArray, day19 has the objects.
Super basic I know just must be a confused morning or something...
thanks for any help
Is day19 actually an instance variable? In the snippet, it's not clear when it's declared as an instance variable or just as a variable outside the scope of the class.
A couple of things:
Are you sure viewDidLoad is the right place to init your array? Confer here.
Also, at least from the code you've got posted, it looks like you're being sloppy with your retains. If your property is a retain type, you should not be writing:
self.myProperty = [[Something alloc] init]; // double retain here, bad
You should instead be writing something like:
self.myProperty = [[[Something alloc] init] autorelease]; // single, good
Also, with
NSObject *newObject = [[NSObject alloc] init];
[day19 addObject:newObject];
unless you have a
[newObject release];
down the pike, you've got a memory leak.
In my viewDidLoad
self.day19 = [[NSMutableArray alloc] init];
In the myMethod where I want to add objects to the array I:
NSObject *newObject = [[NSObject alloc] init];
[day19 addObject:newObject];
However... when i check the day19 array there is nothing in it. If I conversely add the newObject to a tempArray within the myMethod scope and then set the day19 array to the tempArray, day19 has the objects.
Let me guess: You checked the array with code like this:
NSLog(#"day19 contains %lu objects", [day19 count]);
Remember that a message to nil does nothing and returns nil, 0, or 0.0. That's why the output said 0 objects: You don't have an array in the first place. The most probable reason for that is that viewDidLoad hasn't been called yet, so you have not yet created the mutable array.
It's also possible that you have an array (i.e., the view has been loaded) at the time you examine the array, but you didn't have an array yet (the view hadn't been loaded yet) at the time you tried to add to the array, so your addObject: message fell on deaf ears.
Consider creating the array earlier. You probably should be creating it in init or initWithCoder:.
A third possibility is that you examined the array before you ever added to it. Make sure you log or break at both points, so you know which one happened first.
Whatever the problem is, you also need to either assign the array to the instance variable, not the property, or autorelease the array before assigning it to the property. Otherwise, you're over-retaining the array, which means you will probably leak it later on. You probably need to review the Memory Management Programming Guide for Cocoa.