I have the following declarations in my model.h:
#interface Model: NSObject {
NSMutableArray *myMutableArray;
....
}
#property (nonatomic) double myDouble;
The corresponding #synthesize in model.m:
#synthesize myDouble;
I then have the following setter override:
-(void) setMyDouble: (double) newDouble{
myDouble = newDouble;
[myMutableArray addObject:[NSNumber numberWithDouble:myDouble]];
}
Putting a break point after the array assignment, the debugger shows the following for myMutableArray:
myMutableArray = (_NSArrayM *) 0x631c450 1 objects
0 = (NSCFNumber *) 0x631c6a0
So, my double does not seem to be properly getting into the array. I have subsequent assignments to this array for NSStrings that show up fine in the debugger. The values for both myDouble and newDouble are good (usually just an integer).
I've read several threads on assigning doubles to NSMutableArrays and haven't discovered anything out of the ordinary. Any guidance would be appreciated.
Update
It appears that the code is correct, but I failed to understand that the debugger shows the NSNumber's address rather than its value. Thank you everyone for responding, much appreciated! :)
It seems you are confusing with 0 in 0 = (NSCFNumber *) 0x631c6a0. That 0 is the index of the NSNumber in the array. If you retrieve the objects from the array and print it in NSLog, it would show you the correct values. Nothing seems to be wrong in your code.
You forget to allocate your mutable array. Debug your app and see if the array is allocated or not.
Edit
Change your function name to something else and see the magic.
Related
I have an NSMutableArray which is storing a list of other arrays. And when i run the code.
NSLog(#"%#",[[appDelegate teamRoster]objectAtIndex:[indexPath.row]class])
It returns and tells me that i am looking at an Array,
however when i try to do the following
[selectedRowerView tempArray] = [[appDelegate teamRoster]objectAtIndex:[indexPath.row]];
The program errors out. Anyone have any ideas why this might be happening?
You have to understand that [selectedRowerView tempArray] is actually a command / message that is being sent. In C++ equivalent, you are calling selectedRowerView->tempArray() = .... Which doesn't make logical sense because you cannot make an assignment to a function.
What you're trying to do is set the tempArray. If you have the proper setters/getters set-up, you can just run: selectedRowerView.tempArray = ...;
Just make sure that tempArray has a #property and is #synthesize'd.
How about this?
selectedRowerView.tempArray = [[appDelegate teamRoster]objectAtIndex:[indexPath.row]];
…assuming that tempArray is a synthesized property à la
#property (nonatomic, readwrite, retain) NSArray *tempArray;
#synthesize tempArray;
Clarification:
selectedRowerView.tempArray = …;
gets internally processed to
[selectedRowerView setTempArray:…];
which is a setter method.
While
selectedRowerView.tempArray;
gets internally processed to
[selectedRowerView tempArray];
which is a getter method.
Subtle but important difference.
The meaning of foo.bar depends on the very context (enclosing expression) it is used in.
Hopefully I can make this clear, but I am new to Objective-C and to be honest not great with Arrays in the first place.
So, I have a Singleton class (called SingletonState) that I am using to pass variables around my app (please can we leave the whether I should use Singleton classes out of this - I will fix that later). In this class, I have an NSMutableArray (called arrayMyEvents). I have also created a class that I am going to store a list of events (called EventClass). When the user logs in, I call a web service and get back 3 strings. The 3rd string is a comma separated list of value. I parse the data and populate the custom class EventClass. I then add this class to the SingletonState.arrayMyEvents.
I have all of this working. I can go to another ViewController and access the "count" of items in arrayMyEvents.
PROBLEM: I now want to edit one of the ScheduledEventsClass"es" in my array. How do I get access to it and edit some of the properties and update the one in my SingletonState class?
Here is some of the code, that I've tried:
NSString *sWebServiceEvents = [[NSString alloc] initWithFormat:#"%#", [result objectAtIndex:2]];
if ( [ sWebServiceEvents isEqualToString:#"NULL" ] != true ) {
NSArray *arrayEvents = [sWebServiceEvents componentsSeparatedByString:#","];
// If the array has not been initialized they initialize it.
if (sharedState.arrayMyEvents == nil) {
sharedState.arrayMyEvents = [[NSMutableArray alloc ] init ];
}
for (NSString * sEvent in arrayEvents) {
// Set equal to the value of the array (the Event Number) at the same
// position as the row that we are being asked to return a cell/row for.
EventClass *eventClass = [[EventClass alloc] retain];
eventClass.sEvent = sEvent;
[ sharedState.arrayEvents addObject:eventClass ];
}
NSLog(#"LoginView - sharedState.arrayMyEvents Count: %d", [sharedState.arrayMyEvents count]);
}
Here is me trying to access it in another ViewController:
EventClass *eventClass =
[sharedState.arrayMyEvents objectAtIndex:row ];
NSLog(#"eventClass.sEventNumber: ", eventClass.sEventNumber);
eventClass.sLocation = #"Jason's Big Location";
You're going to have some memory leaks from the sEvent loop. [[EventClass alloc]retain] leaves you an uninitialized EventClass object with a reference count of 2. You'll need to change that to [[[EventClass alloc] init] autorelease] to keep it from leaking. The arrayEvents NSMutableArray will retain it during the addObject: call. (Shouldn't that be [sharedState.arrayMyEvents addObject: eventClass] in the loop?)
After that, all you have to do to edit the EventClass object in the second block of code is edit it. The eventClass variable is a pointer to an object in the array. Anything done to that object doesn't affect the pointer referencing it, it affects data referenced by it. The code you have in the second block should change the sLocation of the selected object as you intend.
You have a few more memory leaks in there, too. Use Cmd-Shift-A to build with the static analyzer and it'll tell you where.
Maybe the problem is that you put them in sharedState.arrayEvents but try to take them out of sharedState.arrayMyEvents. Different variables.
Also, lots of memory leaks.
Thanks John and St3fan, your answers and time are appreciated!!!
I think that I figured out my issue:
Basically, the class that I created (EventClass) had the properties setup like this:
#property (nonatomic, assign) NSString *sStudyNumber;
#property (nonatomic, assign) NSString *sTheater;
but, they should be (or at least I got it to work like this):
#property (nonatomic, retain) NSString *sStudyNumber;
#property (nonatomic, retain) NSString *sTheater;
Then, in my second view I was able to do this:
EventClass *eventClass = [sharedState.arrayMyEvents objectAtIndex:row ];
NSLog(#"MyEvents: %#", eventClass.sEventNumber);
eventClass.sLocation = #"Jason's Big Location";
I then checked it in another method of the view using this and it was still there:
EventClass *eventClass = [sharedState.arrayMyEvents objectAtIndex:row ];
NSLog(#"MyEvents: %#", eventClass.sEventNumber);
NSLog(#"MyEvents: %#", eventClass.sLocation);
I also, checked it in yet another view and the value was maintained in the SharedState.arrayMyEvents without issue. :)
In the end, I believe that I boiled down to the difference between "assign" and "retain".
Now, on to the memory leaks :(
Please, let me know if you see any other issues with this.
Thanks,
Jason
for a day now I stare at the following routine and can't get my grips around it. I have a class such as:
MyClass.h
...
#interface MyClass : NSObject {
NSNumber *myNumber1;
NSNumber *myNumber2;
}
#property (nonatomic, retain) NSNumber *myNumber1;
#property (nonatomic, retain) NSNumber *myNumber2;
#end
and the m-file
#import "MyClass.h"
#synthesize myNumber1, myNumber2;
#implementation MyClass
-(id) init {
self = [super init];
NSLog(#"Retain Counts myNumber1: %d, myNumber2: %d", [myNumber1 retainCount], [myNumber2 retainCount]);
myNumber1 = [NSNumber inbitWithint:10];
myNumber2 = [NSNumber inbitWithint:2];
NSLog(#"Retain Counts myNumber1: %d, myNumber2: %d", [myNumber1 retainCount], [myNumber2 retainCount]);
return self;
}
...
I use this class as a globals container and instantiate it from every other class in my app using a
MyClass *myGlobals = [[MyClass alloc] init];
===>>> the weirdo >>>
Running the routine I have the following facinating console output:
Retain Counts (before) - myNumber1: 0, myNumber2: 0
Retain Counts (after) - myNumber1: 1, myNumber2: 26
How can that be?
Do not call `retainCount`
The return value of retainCount can only be considered accurate if you are calling it on an instance of a class you wrote and you have never ever not even once passed said instance to any API provided by the system.
The absolute retain count is an implementation detail for which you might not have any control.
Assuming, for the moment, that your code was typed and, thus, the errors are not really in your original code...
NSNumber caches a subset of common values. That is, for some numeric values, there is a single instance of NSNumber that is returned for all requests to retrieve an NSNumber instance wrapping that number.
If this is your actual code, it shouldn't work at all, it should simply crash. If not, you should cut and paste your actual code.
However, a couple of things.
First, if you use an NSNumber as an ivar, like anything else, you must take ownership of it. If you plan to use a convenience constructor, you must either assign it using the property on self, or send it an explicit retain message.
Second, you typed something like initWithInt: here. If you are actually using that message, then you have never actually allocated the number in the first place. You must replace this with one of the following:
myNumber1 = [[NSNumber alloc] initWithInt:10]; // explicitly create the number
myNumber1 = [[NSNumber numberWithInt:10] retain]; // take ownership through retain
[self setMyNumber1:[NSNumber numberWithInt:10]]; // use the property accessors to deal with ownership and the convenience constructor to create the number
However you choose to do it, you must at some point take ownership of the object.
You should never even look at retainCount as it carries little significance anyway. The reason you see the count of 26 is that probably somewhere in the frameworks (or even in your own app) other instances of NSNumber exist that are created with the same int 2. An NSNumber is immutable, and so as an optimization NSNumber probably just gives you back an instance it has created earlier. As long as you don't look at retainCount it doesn't matter to you.
OK, This is a method from my program that keeps giving the EXC_BAD_ACCESS error and crashing. I indicated the line below. questionsShown is a readwrite property and points to an NSMutableArray that I initialize with a capacity of 99 at an earlier point in the program. When I debug everything appears normal in terms of the property being allocated. I assumed there must be some issue with memory management but I am having serious trouble finding the problem. Thanks in advance for any help.
#synthesize questionList;
#synthesize questionLabel;
#synthesize questionsShown;
-(IBAction)next{
int numElements = [questionList count];
int r;
if (myCount == numElements){
[questionLabel setText:#"You have seen all the questions, click next again to continue anyways."];
[questionsShown release];
questionsShown = [[NSMutableArray alloc] initWithCapacity:99];
myCount = 0;
}
else {
do {
r = rand() % numElements;
} while ([questionsShown indexOfObjectIdenticalTo:r] != NSNotFound);
NSString *myString = [questionList objectAtIndex:(NSUInteger)r];
[questionLabel setText:myString];
myCount++;
[questionsShown addObject:r]; //results in crash with message EXC_BAD_ACCESS
myCount++;
}
}
The EXC_BAD_ACCESS is coming from dereferencing r, which is just an integer. Your compiler should be giving you a warning (make pointer from integer without a cast) on that line.
If questionsShown is supposed to be some kind of index set for you (which it appears to be), you might want to either use that class, or you will have to box your integer in an NSNumber object. So:
[questionsShown addObject:[NSNumber numberWithInt:r]];
and when you read it:
[questionsShown indexOfObjectIdenticalTo:[NSNumber numberWithInt:r]]
I recommend, however, that you take a look at the NSIndexSet documentation.
With a mutable index set, you could do:
[questionsShownIndexSet containsIndex:r]
and
[questionsShownIndexSet addIndex:r]
I declared
NSString *dayinfield[43];
and fill it in
-(void)DrawDemo {
dayinfield[2] = #"hallo";
dayinfield[3] = #"test";
// also i can read it
NSLog (#"show: %#",dayinfield[2]);
//works fine
}
but when i like to read its content in another function (same class)
-(void)ReadData
{
NSLog (#"show: %#",dayinfield[2]);
// I get random infos or “EXC_BAD_ACCESS
}
How do I initialize the NSString Array correct so I can reach its content in each of my functions??
Thanks
chris
If you only assign literals to the array elements, this should not be a problem. But if you use other strings, you have to retain the instances manually when using a C array.
By the way: Objective-C methods start with a lowercase letter.
This would happen if you never initialized the array (or the parts of it you are accessing) - if you haven't called -DrawDemo before -ReadData or used different indices than the ones posted here, the array would simply contain garbage values.
Try to initialize the array contents to nil or #"" in your initializer method and see if the problem persists.
Alternatively consider using a suitable Cocoa container.
It's memory is probably being released before your second call. Assuming you have declared dayinfield as an ivar (and the fact that you don't get bad access all the time) your string aren't properly retained.
Initialise the strings like this:
dayinfield[2] = [[NSString alloc] initWithString:#"hallo"];
dayinfield[3] = [[NSString alloc] initWithString:#"test"];
and you should release them after you're class is being deallocated (See Memory Management Guide).
Also, obviously it depends on what you want to do, but it might be easier if you use NSArray instead of C arrays.
What you have in the OP should work although it is an exercise in sheer masochism to use old school C arrays with objects.
I ran this code:
#interface TestClass : NSObject {
NSString *a[1];
}
- (void) drawDemo;
- (void) readData;
#end
#implementation TestClass
- (void) drawDemo{
a[0]=#"A Zero";
a[1]=#"A One";
}//------------------------------------- (void) drawDemo------------------------------------
- (void) readData{
NSLog(#"a[0]=%#,a[1]=%#",a[0],a[1]);
}//------------------------------------- (void) readData------------------------------------
#end
TestClass *tc=[[TestClass alloc] init];
[tc drawDemo];
[tc readData];
... and got this output:
a[0]=A Zero,a[1]=A One
Your problem is elsewhere in your code. There is no compelling reason to use C arrays with objects. You gain nothing and you have to watch them like a hawk to prevent errors.