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
Related
I am write a Objective-C Code on XCode 4.4.
I have a NSMutableArray as a instance variable of my class k_info
I have defined and synthesized (nonatomic,retain) property by the name of onesplaces too.
I am unable to add a NSMUtableString object in the NSMutableArray onesplaces.
When I try to add it.The size of onesplaces remains 0 and object at zero index obviously remains null.
I tried doing this with and without using "self" key-word but it didnt worked in either case.
My syntax of adding object and printing it is right because when I create a new NSMutableArray test
and try to do the same thing it works for it but not for the instance variable onesplaces.
I cannot proceed any further in my project without solving this issue.please tell me why is it
happening and how should I solve this problem.
-(void)createinfo:(NSMutableArray )al varsis:(int)vars
{
NSMutableString stes=[[NSMutableString alloc]init];
stes=(NSMutableString*)#"string0";
[ onesplaces addObject:stes];
NSLog(#"%u",[onesplaces count]);
NSLog(#"value is: %# ",[ onesplaces objectAtIndex:0]);
[ self.onesplaces addObject:stes];
NSLog(#"%u",[onesplaces count]);
NSLog(#"value is: %# ",[self.onesplaces objectAtIndex:0]);
NSMutableArray* test=[[NSMutableArray alloc]init];
[ test addObject:stes];
NSLog(#"%u",[test count]);
NSLog(#"value is: %# ",[test objectAtIndex:0]);
}
You probably forgot to create the array. Somewhere in your code, maybe in your init method, you need to create the array before using it.
self.onesplaces = [[NSMutableArray alloc] init];
You get nil instead of error messages because Objective-C allows you to send messages to nil, which always return nil.
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'
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.
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