How to initialize the NSArray in ARC? - objective-c

I tried initializing the array :
In .h file
#property (nonatomic, retain) NSArray *accounts;
In .m file :
#synthesize accounts;
- (void)viewDidLoad
{
[super viewDidLoad];
NSArray *arrList = [acAccountStore accountsWithAccountType:accountType];
// This returns array
self.accounts = [NSArray arrayWithArray:arrList]; // I tried debug after
// this and it gives me data in debugger.
// Note array List have 3 data in it.
}
Now On button click i call a method:
- (IBAction) ButtonClicked :(id) sender {
NSLog(#" data : %#",[self.accounts objectAtIndex:0]); // Breaks at this point.
// When i tried with debug it gives me (no Objective-C description available)
}
Is the initialization of array correct Or If the code is not right please let me know.
Main concern is when i do debug in viewDidLoad, the self.accounts show me proper values. But after doing the click event its empty and throws EXEC_BAD_ACCESS error.
Thanks for help in advance

hm looks fine. A couple of questions then:
Where are you calling the self.accounts = [NSArray arrayWithArray:arrList];
I assume that the array is being setup before your button is being pressed?
There's no real reason that arc should be clearing out the variable. Have you set a strong reference to it or a weak one? If you're using self. on a variable, you should have :
#property (nonatomic, strong) NSArray *accounts;
or similar to that in the .h file and then
#synthesize accounts;
in the .m file.
If you've got weak instead of strong then ARC may possibly clear the memory but it still shouldn't.

Update:
Create a property for your account store as well. I had this exact issue recently and this fixed it.
#property (nonatomic, strong) ACAccountStore *accountStore;
Original Answer
Because you're using ARC, you need to change your property declaration from
#property (nonatomic, retain) NSArray *accounts;
to:
#property (nonatomic, strong) NSArray *accounts;
With the latest LLVM compiler, you don't need to synthesize properties either. So you can remove #synthesize accounts.
You should always use defensive coding as well, so in your - buttonClicked: method, you should do:
- (IBAction)buttonClicked:(id)sender {
if (self.accounts) {
NSLog(#"data: %#", [self.accounts objectAtIndex:0]);
}
}
This makes sure that the pointer to the array is valid.
You can also check to make sure an item in an array exists before trying to read it by doing:
- (IBAction)buttonClicked:(id)sender {
if (self.accounts.count > 0)
NSLog(#"data: %#", [self.accounts objectAtIndex:0]);
}
}

Related

Problems with an NSMutableArray

I'm trying to write an app that has two scenes in it. The first page is a UITableView that will contain a list of note entries. The second scene has 2 text fields (note summary and note description). I'm entering details on the second scene and then clicking a "Save" button which saves the data:
NoteListViewController.m
- (IBAction)saveAndGoBack:(id)sender {
NSLog(#"NoteDetailViewController.m: %#", NSStringFromSelector(_cmd));
NSString * desc = [[NSString alloc]init];
NSString * detail = [[NSString alloc]init];
desc = _noteTitle.text;
detail = _noteDesc.text;
[[NoteStore sharedStore]createNoteWithDesc:desc AndDetail:detail];
[self.navigationController popViewControllerAnimated:YES];
}
NoteStore is a static sharedStore that I am saving the data into.
NoteStore.m
-(Notes *)createNoteWithDesc:(NSString *)desc AndDetail:(NSString *)detail {
NSLog(#"NoteStore.m: %#", NSStringFromSelector(_cmd));
Notes * newNote = [[Notes alloc]initNoteWithDesc:desc AndDetail:detail];
[self.privateItems addObject:newNote];
return newNote;
}
So, the note is added to an NSMutableArray called "privateItems". I confirmed that the Note object gets added properly.
*****The problem happens when I try to retrieve the Note object (desc and detail) from the privateItems array later on using an accessor method which has a public property in the NoteStore.h file called allItems (it's an NSArray readonly, nonatomic and a copy):
NoteStore.m
-(NSArray *)allItems{
NSLog(#"NoteStore.m: %#", NSStringFromSelector(_cmd));
return [self.privateItems copy];
}
Everytime I try to retrieve it, the first property (desc) comes up as nil while the second property (detail) has the data I saved in the second text field of the second scene. Why is the first field constantly coming up as nil???
Just for clarity, a Note object is declared as follows
#interface Notes : NSObject
// What are the properties of a note?
#property (nonatomic, weak) NSString * noteDesc;
#property (nonatomic, weak) NSString * noteDetail;
#property (nonatomic, weak) NSString * test;
// Designated Initializer
-(instancetype)initNoteWithDesc:(NSString *)desc AndDetail:(NSString *)detail;
#end
Any help would be greatly appreciated.
When you call the designated initialiser you pass in two NSString objects. At this point they are owned by the method where they are created.
When they are assigned to the properties they only have a weak reference and therefor the retain count is not bumped up. Weak references are good for things like delegate objects. In this case you want your objects to stick around, so by declaring them as strong you're saying I want these properties to stick around in memory and take ownership of them.

ARC - ObjC Objects with CF instance variables

I think I'm being a bone head here...
The static analyzer complains in the -(void)doSomethingInteresting method:
Potential leak of an object stored into myAddressBook
Well, sure, that makes sense; I'm calling a create function without a matching release. But, I don't think I want to release myAddressBook at the end of -doSomethingInteresting because I want it to stick around for the life of the AwesomeObject instance.
AwesomeObject.h
#interface AwesomeObject : NSObject
#property (assign, nonatomic) ABAddressBookRef addressBook;
#end
AwesomeObject.m
#implementation AwesomeObject
- (void)doSomethingInteresting
{
CFErrorRef error = NULL;
ABAddressBookRef myAddressBook = ABAddressBookCreateWithOptions(NULL, &error);
[self setAddressBook:myAddressBook];
}
#end
EDIT: Screen shot attached
The analyzer doesn't understand you wish to assign a retained address book in your property, and thus not release it at the end of doSomethingInteresting.
Change your property to:
#property (strong, nonatomic) id addressBook;
and set it like so:
[self setAddressBook:CFBridgingRelease(addressBook)];
Now, when you want to use the addressBook property, use the (__bridge ABAddressBookRef) cast.
Also, you need to release a potential CFErrorRef object, which may have been created during ABAddressBookCreateWithOptions:
if(error)
{
CFRelease(error);
error = NULL;
}
You need to call it like this:
[self setAddressBook:CFBridgingRelease(myAddressBook)];

Objective C Adding custom objects into NSMutableArray

I want to store a list of data records in a NSMutableArray for use in a UITableView. In other languages I would have used a simple 'type' structure to define the record structure but I understand the way to do this in Obj-C is to define a new class. I've done this as follows :
#interface CustSuppListItem : NSObject
#property (nonatomic, copy, readwrite) NSString *acCode;
#property (nonatomic, copy, readwrite) NSString *acCompany;
#property (nonatomic, copy, readwrite) NSString *acContact;
#property (nonatomic, assign, readwrite) double osBalBase;
#property (nonatomic, assign, readwrite) unsigned int acAccStatus;
#end
#implementation CustSuppListItem
#synthesize acCode, acCompany, acContact, osBalBase, acAccStatus;
#end
In the viewDidLoad of my UITableViewController I instantiate the array :
tableListDataArray = [[NSMutableArray alloc] init];
Once I have retrieved my data, I add it to the array as follows :
CustSuppListItem *custSuppItem = [[CustSuppListItem alloc] init];
[custSuppItem setAcCode:[jsonCustSuppRecord getStringForKey:#"acCode"]];
[custSuppItem setAcCompany:[jsonCustSuppRecord getStringForKey:#"acCompany"]];
[custSuppItem setAcContact:[jsonCustSuppRecord getStringForKey:#"acContact"]];
[custSuppItem setOsBalBase:[jsonCustSuppRecord getDoubleForKey:#"osBalBase"]];
[custSuppItem setAcAccStatus:[jsonCustSuppRecord getIntForKey:#"acAccStatus"]];
[tableListDataArray addObject:custSuppItem];
[custSuppItem release];
In my table cellForRowAtIndexPath method, I retrieve the data for the current cell as follows:
CustSuppListItem *listDataRecord = [tableListDataArray objectAtIndex:indexPath.row];
[cell.lblCompanyName setText:listDataRecord.acCompany]; // EXC_BAD_ACCESS here
[cell.lblAcCodeContact setText:[NSString stringWithFormat:#"%#, %#",
listDataRecord.acCode, listDataRecord.acContact]];
[cell.lblBalance setText:[Utils fmtNumber:listDataRecord.osBalBase withDecPlaces:2]];
[cell.lblStatus setText:[Utils exchAccStatusDesc:listDataRecord.acAccStatus]];
return cell;
In the dealloc method for the view controller I release the NSMutableArray :
[tableListDataArray release];
I'm very new to Obj-C so it would be great if somebody could confirm everything I've done so far makes sense and is in order. I am getting an intermittent EXC_BAD_ACCESS error when trying to read the acCompany property (see comment next to line) so something must not be right.
Any help appreciated,
Jonathan
All your code looks reasonable and correct to me at first glance.
A few things that I would look at are:
Confirm that cell definitely has a property lblCompanyName. If you're trying to assign to a property that doesn't exist then you will get this type of error. Have you defined a custom cell object type?
Confirm that it is always the acCompany property that is causing the EXC_BAD_ACCESS, and not just any property on the object. One way to do this would be to change the ordering of the lines in the cellForRowAtIndexPath method.
Confirm that the listDataRecord that's causing the crash is getting populated correctly in the first place. In other words, confirm that your jsonCustSuppRecord is always valid. What does jsonCustSuppRecord getStringForKey: return if the key doesn't exist in the jsonCustSuppRecord?
Set a breakpoint at this line: [tableListDataArray addObject:custSuppItem]; and examine the contents of the custSuppItem each time (this is an extension of point 3. above)

addObject in NSMutableArray doesn't work

I'm a beginner to XCode.
Below is my code. I want to add an object to a mutablearray. From the debugger window I can see there is one object added to the array "words". I can also see the property "flag" of that object is "NO". The problem is another property "str" is shown as "out of scope".
Can anyone help me with this issue? Thanks a loooooot! Stucked on this one for the whole afternoon.
NSMutableArray * words=[[NSMutableArray alloc] initWithCapacity:numberOfWords];
Word *w=[[Word alloc] init];
[w setStr:#"abc" flag:NO];
[words addObject: w];
[w release];
--
#interface Word : NSObject{
NSString *str;
BOOL flag;
}
-(void) setStr: (NSString *) s flag:(BOOL) b
{
self.str=s;
flag=b;
}
Do you have a property declaration for your string? Are you retaining the string you are setting?
Still AFAIK 'out of scope' does not necessarily mean it was not set or that nothing has been set. Try an NSLog of the value or something. You might find that there is nothing wrong.
Have a look at this question that talks about scope in GDB:
Objective-C: instance variables out of scope in debugger
Your problem is that the string #"abc" is a temporary object who's scope only exists during the [w setStr:#"abc" flag:NO] method call. You should be able to resolve this problem by making str a #property of Word:
#interface Word : NSObject{
NSString *str;
BOOL flag;
}
#property (retain) NSString* str;
#end
And in your implementation file
#implementation Word
#synthesize str;
-(void) setStr: (NSString *) s flag:(BOOL) b
{
self.str=s;
flag=b;
}
#end

Objective-C NSArray

I'm new to Obj-C and iPhone SDK. The test application I'm stock with is a color switcher containing two buttons ("Back", "Forward") and one text label. The idea is to switch between rainbow colors (background) and setting an appropriate text label in a cyclic manner.
I declared NSArray (which is to contain colors names) in RainbowViewController.h, synthesized it in RainbowViewController.h and I can't add any string into that array.
This is "h" file:
#import <UIKit/UIKit.h>
#interface RainbowViewController : UIViewController {
IBOutlet UILabel *currentColorTextLabel;
NSArray *colorsArray;
NSString *msg;
}
#property (nonatomic, retain) IBOutlet UILabel *currentColorTextLabel;
#property (nonatomic, retain) NSArray *colorsArray;
#property (nonatomic, retain) NSString *msg;
- (IBAction) pressForwardButton;
- (IBAction) pressBackButton;
#end
This is "m" file:
#import "RainbowViewController.h"
#import <Foundation/Foundation.h>
#implementation RainbowViewController
#synthesize currentColorTextLabel;
#synthesize colorsArray;
#synthesize msg;
int currentArrayIndex = 0;
colorsArray = [[NSArray alloc] init]; //here i get "Initializer element is not constant" error message
[coloursArray addObject:#"Red"]; //here I get "Expected identifier or '(' before '[' token"
[coloursArray addObject:#"Orange"];
//etc
- (IBAction) pressForwardButton {
//here I'm going to increment currentArrayIndex, set an appropriate color, and update a currentColorTextLabel based on currentArrayIndex.
}
- (IBAction) pressBackButton {
}
//auto-genereted code here
#end
I'm new to obj-c as well, but I think you need to initialize the array with objects, or use an NSMutableArray if you want to add objects after it is created.
You have the code that should go in your init method just sitting out in the middle of the file. You can't set instance variables like that.
jasongetsdown is correct. You need to instantiate the NSArray object with the objects it will contain and nil terminated.
#"Red", #"Blue", nil
If you wish to have an array that you can change you need to make it a Mutable Array.
However, you have another problem here. Your property that you are synthesizing and allocating for is an object named colorsArray and you are trying to pass a method to a coloursArray object, two different spellings.