Alright so I am a little new to the NSMutableArray class and I think I am missing something obvious. I have an object pass a NSMutable Array to my window controller like so in my.m:
summaryWindow = [[SummaryWindowController alloc] init];
[summaryWindow setGlobalStatusArray:globalStatusArray];
I have the receiver method in the summaryWindow object as so:
-(void)setGlobalStatusArray:(NSMutableArray *)myArray
{
if ([myArray count] >0) {
if (globalStatusArray) {
[globalStatusArray release];
}
globalStatusArray = [[NSMutableArray alloc] initWithArray:myArray];
NSLog(#"Summary Window Init with new array: %#",globalStatusArray);
I see the NSLog no problem, and in that same object (summaryWindow) I have the following method:
- (NSMutableArray *)getGlobalStatusArray
{
return globalStatusArray;
}
Now I have globalStatusArray declared in my .h file as
NSMutableArray *globalStatusArray;
So shouldn't This be retained because I am using: initWithArray?
When I try to access this value in an another IBAction method:
- (IBAction)refreshButtonClicked:(id)sender
{
NSLog(#"The user has clicked the update button");
[ aBuffer addObjectsFromArray: globalStatusArray];
NSLog(#"Buffer is currently:%#",aBuffer);
[tableView reloadData];
}
The NSMutable array is null
2011-08-18 10:40:35.599 App Name[65677:1307] The user has clicked the update button
2011-08-18 10:40:35.600 App Name[65677:1307] Buffer is currently:(
)
I have tried using my own method to get the value i.e. [ self getGlobalStatusArray] to but I am missing something huge. FYI aBuffer is also declared in my .h ,
As albertamg noted, that looks like an empty array rather than nil, and a released object doesn't magically become nil under normal circumstances anyway.
This smells strongly of two different objects. Try logging self in your methods and see if one instance is getting the array and another is interacting with the UI.
This code isn't doing anything useful:
if ([myArray count] >0) {
if (globalStatusArray) {
[globalStatusArray release];
}
globalStatusArray = [[NSMutableArray alloc] initWithArray:myArray];
If the count of the old array is zero, it's leaking the actual array object. If the count is not zero, then it's releasing it properly. Just do the release and don't bother counting.
Are you sure there's actually something in myArray?
joe
Related
I have searched online and am at a loss.
I have a text field and when a user types something in and presses 'return' the text will save to my NSMutablearray (userAnswers)
NSMutableArray *userAnswers;
in my init method I have allocated the array:
userAnswers = [[NSMutableArray alloc] initWithObjects:#"Test", nil];
have also tried:
userAnswers = [[NSMutableArray alloc] init];
//When the user presses 'return' on keypad
- (BOOL)textFieldShouldReturn:(UITextField *)textField {
[answerText resignFirstResponder];
if (levelSelected == 1) {
[userAnswers insertObject:answerText.text atIndex:0];
[userAnswers replaceObjectAtIndex:0 withObject:answerText.text];
//Have tried both of these!
NSLog(#"SHOULD INSERT INTO ARRAY");//This prints because level one is selected
}
NSLog(#"ARRAY: %#", userAnswers); //Just print null
}
I have no idea what I am doing wrong??
Thanks for any help!
It looks like your array is not allocated at the moment of the insertion and it even prints this (as you commented). You should allocate the array before putting there anything. Your allocation has to be placed in the wrong place so at the returning stage the array is nil or you are assigning nil to the array reference at some point. The reason the array is nil may also depend on how you declared that ivar. This is what I can say on the basis of this code sample.
I think your array is not allocated when the function is call so you can try to alloc your array in viewDidLoad:.
And also decleare your array in .h file not in init or viewDidLoad:
If you are using storyboard allocate array in initWithCoder instead init.
Initializing a View Controller
My goal is to add a string to array, and I do that in a method which I call.
In this method, I get a null value in the array, and don't know why. I have this at the start of my class:
NSMutableArray *listOfEvents;
and a method which I call on each event:
-(void)EventList
{
[listOfEvents addObject:#"ran"];
NSLog(#"%#", listOfEvents);
}
I get (null) in the log.
If I put the array definition NSMutableArray *listOfEvents; in the function body, I get the string value #"ran", each time, so the array always has only one value, instead of having many strings named #"ran".
What's wrong with this? It seems that I can't understand something about arrays, even though I have read the documents a number of times.
I'm assuming you haven't initialized listOfEvents.
Make sure you do listOfEvents = [[NSMutableArray alloc] init]; in your class's init method. Also make sure you release it in your class's dealloc method.
If you're getting nil in your log message, you need to make sure listOfEvents is non-nil before adding your object. IE:
-(void)EventList
{
if (listOfEvents == nil) {
listOfEvents = [[NSMutableArray alloc] init];
}
[listOfEvents addObject:#"ran"];
NSLog(#"%#",listOfEvents);
}
In Objective-C, messages with void return types sent to nil go to absolutely-silent nowhere-land.
Also, for the sake of balance, be sure you have a [listOfEvents release] call in your dealloc implementation.
Apparently you're not initializing your array.
NSMutableArray *listOfEvents = [[NSMutableArray alloc] init];
If that's your problem, I suggest reading the docs again. And not the NSMutableArray docs. Go back to The Objective-C Programming Language and others.
You need to alloc the NSMutableArray. Try doing this first -
NSMutableArray *listOfEvents = [[NSMutableArray alloc] init];
After this you could do what you what you planned...
So I had this code, and it did not work:
for (NSDictionary *item in data){
[self.resultsArray addObject:item];
}
self.resultsArray is nil. But then I changed it to this:
NSMutableArray *myDataArray = [[NSMutableArray alloc] init];
for (NSDictionary *item in data){
[myDataArray addObject:item];
}
self.resultsArray = myDataArray;
[myDataArray release];
and now it worked. self.resultsArray is now populated
So I'm a beginner in Objective C and I was wondering why can I not just directly use it in the property's addObject. Why did I have to create another mutable array, populate it, assign it to the resultsArray property and release the mutable array I made?
Thanks in advance!
EDIT: Also, in a lot of books I've been working on, this is done a lot.
simple answer
You didn't initialize self.resultArray before adding objects to it. It is just a pointer to the value which is nil until you alloc it.
self.resultArray = [[NSMutableArray alloc] init]; before adding objects to it will solve the issue.
However, this way of alloc'ing will create a memory leak, therefore it is not shown in books and examples. Memory leak can happen if the self.resultArray property is marked as retain and by calling alloc it will be retained 2 times.
If self.resultsArray is nil, then [self.resultsArray addObject:item] will NOT add an object to the array, it will just do nothing (because the array will be nil by default, and sending messages to nil is a no-op in Objective-C). When you create a mutable array as a local variable, you can add things to it — then if you assign it to the property, well, everything works as you expect and self.resultsArray will no longer be nil.
Typically when you have properties like this, you'd set them up in your init method:
- (id)init {
// ...
self.resultsArray = [NSMutableArray array];
// or access the ivar directly:
// _resultsArray = [[NSMutableArray alloc] init];
// ...
}
Then as soon as your object is initialized you'll be able to add things to the array. Again, if you don't do this, it will be nil by default, and [self.resultsArray addObject:item] will have no effect.
Chances are you are not initializing the array (I'm going to assume myDataArray is an NSMutableArray).
In your init method, call myDataArray = [NSMutableArray array]; and it'll work
The important thing to note is that you're not creating another mutable array as you didn't have an array to start with. Merely declaring a property or variable does not create an object to go along with it. That's why self.resultsArray starts out as nil.
The working code you have is designed to allow you to explicitly release the array as you are retaining it twice: once when you alloc it and once when you assign it to your property. You only want one of those retains, so you release once.
You could just do:
self.resultsArray = [[NSMutableArray alloc] init];
[self.resultsArray release];
for (NSDictionary *item in data){
[self.resultsArray addObject:item];
}
This is less code, but it's not as clear. Clarity is important.
I am currently trying to write a class to create faux grid system to keep track of a NSMutableArray of game entities using a NSMutableArray of NSMutableArrays. Given my limited experience with Objective-C programming, I am unsure of how certain things work.
Here is the init method:
#define MAX_BALL_ROWCOUNT 6
#define MAX_BALL_COLCOUNT 4
- (id) initWithMutableArray:(NSMutableArray *)aList {
self = [super init];
if (self != nil) {
ballList = [[NSMutableArray alloc] initWithCapacity: MAX_BALL_ROWCOUNT];
for (int i=0; i<MAX_BALL_ROWCOUNT; i++) {
NSMutableArray *balls = [[NSMutableArray alloc] initWithCapacity:MAX_BALL_COLCOUNT];
[ballList addObject:balls];
[balls release];
}
int x = 0;
for (NSMutableArray *array in ballList) {
for (int i = 0; i<MAX_BALL_COLCOUNT; i++) {
[array addObject:[aList objectAtIndex:x]];
x++;
}
}
}
return self;
}
ballList is the class's NSMutableArray that will store NSMutableArrays.
aList is the NSMutableArray containing the GameEntities I wish to keep track of that is passed into this class.
All the sizes and amount of entities to store are fixed, which is why there is no checks on the sizes of the arrays nor the number of entities to store.
So the first question I have involves freeing memory. This is the dealloc function I currently have:
- (void) dealloc {
[ballList release];
[super dealloc];
}
Does calling a release on ballList cause the release to be called on the NSMutableArrays that it contains (which will subsequently call the release on the objects those NSMutableArrays contain) or do I have to write something like:
for (NSMutableArray *array in ballList) {
[array release];
}
[ballList release];
My second question involves the usage of this array of arrays. Is this the proper way to traverse through ballList?
- (void) update {
for (NSMutableArray *array in ballList) {
for (GameEntity *balls in array) {
(CGPoint) location = [balls getLocation];
[balls setLocation: CGPointMake(location.x+1, location.y+1)];
}
}
}
Lastly, in the code above where it sets the balls location, does it only affect the contents within ballList or does the original aList that is passed into ballList change as well? If the contents in the original aList do not change, how would I write it so that they do?
If people have suggestions for a better way to keep track of the entities in a grid system, I'd be open to those too. Thanks in advance.
First : One release is enough for the NSMutableArray instance to release all it's object.
[ballList release];
Second : Your code for updating GameEntity instance is fine and will also effect to the original aList (which you called) .
When the dealloc of a NSArray or NSMutableArray is called, all its contents gets a release message. So when you release ballList, if there there is no other owner (I guess in this case there is none) then its dealloc is called and you don't need to release the other arrays here.
Your loop traversal is fine. Though for 2D arrays instead of NSArray of NSArray I personally prefer pure C 2D array, at least in most of the cases.
When you are adding object in this way you are adding a reference in the array. So any change via the array's reference will be reflected in all references of the object. If you don't want that then add a copy of the object in the array.
i've a function like this:
#property(nonatomic,retain) NSMutableArray *array;
#synthesize array = _array;
(NSMutableArray *) name
{
self.array = [[NSMutableArray alloc]init];
[_array addObject:object];
[object release];
return [_array autorelase];
}
In the other function i've a property like the property above, named result, and i make:
self.result = [... name];
Then in dealloc i make
[_result release];
and it crashes in this point, how can i solve this?
I've tried many roads, but or it crashes, or i see memory leak in Instruments, where am i wronging?
Thanks.
While there's a lot wrong with this code, the likely cause of your crash is that you're releasing object within -name without taking ownership of it- unless you're creating object within the method through a call to -alloc, -new, or -copy, that method doesn't own it and isn't responsible for releasing it. This is causing that object to be invalid within the NSMutableArray, so when _result releases, it attempts to release an invalid piece of memory and crashes.
Also, properties aren't simply local variables for individual functions, they're member variables for instances of the class for which you're writing these classes. If your end goal is only to return an autoreleased array and set it to result you could do the following:
- (NSMutableArray *) name {
//call a convenience method- it comes back autoreleased
NSMutableArray* theArray = [NSMutableArray array];
[theArray addObject:object];
//don't release object unless you took ownership of it in this function
return theArray;
}
then outside the function, either call self.result = [... name] or [self setResult:[... name]];
You have a very strange method definition (the header should have a - before the return type), and inside that definition you are accessing a variable called object that doesn't seem to exist. I'm not sure what you want, but you've got at least one memory problem. The array that you create in name gets leaked every time the method is called. If you add some details, like the crash message, someone may be able to help more.