CODEWITHSUNDEEP
iphoneobjective-cuitableview
Fred
Fred

Reputation:

Problem to populate a Tableview on iPhone

Code N°1:

NSMutableArray *arrayTmp = [[NSMutableArray alloc] initWithObjects:nil];

[arrayTmp addObject:@"line 1" ];
[arrayTmp addObject:@"line 2" ];

self.list = arrayTmp;
[self.tableView reloadData];
[super viewDidLoad];
[arrayTmp release];

Code N°2:

NSMutableArray *arrayTmp = [[NSMutableArray alloc] initWithObjects:nil];

NSString *fieldName = [[NSString alloc] init];
fieldName = [NSString stringWithFormat:@"%@",@"Ligne1"];
[arrayTmp addObject:(NSString *) fieldName];
[arrayTmp addObject:@"line 2" ];

self.list = arrayTmp;
[self.tableView reloadData];

[super viewDidLoad];
[arrayTmp release];

Codes N°1 & N°2 do exactly the same job: they populate a tableview. My problem is with the code N°2:he displays the tableView but if I move the tableView with the finger, the iphone freeze. The Debugger shows the following message: "GDB:Program receive signal: "EXC_BAD_INSTRUCTION". I don't see what it is wrong. Has someone an idea of the problem ? Thank you in advance.

Upvotes: 1

Views: 1509

Answers (5)

Umangshu Chouhan
Umangshu Chouhan

Reputation: 131

self.list=[NSArray arrayWithArray:arrayTmp];

Just allocate self.list . This is craeting bad exec. Because you are not allocating memory to list.

Retaining will not solve the problem

Upvotes: 0

Fred
Fred

Reputation:

Thank you for your replies.

At the end, I resolve my problem by:

-adding a "retain" to my NNString fieldName

-removing a "release" on a variable in the tableView method "cellForRowAtIndexPath"

Thank again for your helpfull support !

Upvotes: 0

lostInTransit
lostInTransit

Reputation: 71047

Here's how you should use code 2

NSString *fieldName = [[NSString alloc] initWithString:@"Ligne1"];
NSMutableArray *arrayTmp = [NSMutableArray arrayWithObjects:fieldName, @"line2", nil]; //I would suggest using @"Ligne1" instead of fieldName if possible

self.list = [arrayTmp retain]; //This will make sure even after releasing arrayTmp, list is not affected
[self.tableView reloadData];

[arrayTmp release];

Upvotes: 0

Fred
Fred

Reputation:

Thank you for your very good advices. As you suggest, I retain the array in my @property:

  @property (retain) NSArray *list;

If in my code I put:

 NSString *fieldName = [[[NSString alloc] initWithString: @"line 1"] retain];
[arrayTmp addObject:fieldName];
[arrayTmp addObject:@"line 2" ];

it's working!

But if I put:

NSString *fieldName = [[[NSString alloc] initWithString: [NSString stringWithFormat: @"line 1"] ] retain];
[arrayTmp addObject:fieldName];
[arrayTmp addObject:@"line 2" ];

it's display well the tableview but if I move the tableView 2 or 3 times with the finger, the iphone freeze.And unfortunately, I need to use stringWithFormat & stringWithUTF8String in order to populate my tableView from a database.

The error is still "EXC_BAD_ACCESS". But I don't know how to perform a backtrace. The Debugger shows:

0 0x300c8c18 in objc_msgSend

1 0x30b524dc in -[UILabel text]

2 0x30c07b44 in -[UITableViewCell layoutSubviews]

3 0x30a74020 in -[UIView(CALayerDelegate) _layoutSublayersOfLayer:]

4 0x31dd20f0 in -[CALayer layoutSublayers]

5 0x31dd2000 in CALayerLayoutIfNeeded

6 0x31dd1774 in CAContextCommitTransaction

7 0x31dd143c in CATransactionCommit

8 0x3026a0ec in __CFRunLoopDoObservers

9 0x30269920 in CFRunLoopRunSpecific

10 0x30269326 in CFRunLoopRunInMode

11 0x31563e60 in GSEventRunModal

12 0x30a4feb8 in -[UIApplication _run]

13 0x30a5961c in UIApplicationMain

14 0x000020bc in main at main.m:14

asm obj_msgSend 0x300c8cc04:1 0x300c8c04 <+0000> teq r0, #0 ; 0x0

0x300c8c08 <+0004> moveq r1, #0 ; 0x0

0x300c8c0c <+0008> bxeq lr

0x300c8c10 <+0012> stmdb sp!, {r3, r4, r5, r6}

0x300c8c14 <+0016> ldr r4, [r0]

0x300c8c18 <+0020> ldr r5, [r4, #8]

0x300c8c1c <+0024> ldr r6, [r5]

0x300c8c20 <+0028> add r3, r5, #8 ; 0x8

0x300c8c24 <+0032> and r5, r6, r1, lsr #2

0x300c8c28 <+0036> ldr r4, [r3, r5, lsl #2]

0x300c8c2c <+0040> teq r4, #0 ; 0x0

0x300c8c30 <+0044> add r5, r5, #1 ; 0x1

0x300c8c34 <+0048> beq 0x300c8c54

0x300c8c38 <+0052> ldr ip, [r4]

0x300c8c3c <+0056> teq r1, ip

0x300c8c40 <+0060> and r5, r5, r6

0x300c8c44 <+0064> bne 0x300c8c28

0x300c8c48 <+0068> ldr ip, [r4, #8]

0x300c8c4c <+0072> ldmia sp!, {r3, r4, r5, r6}

0x300c8c50 <+0076> bx ip

0x300c8c54 <+0080> ldmia sp!, {r3, r4, r5, r6}

0x300c8c58 <+0084> b 0x300c8c5c

Upvotes: 0

Andrew Grant
Andrew Grant

Reputation: 58804

My guess would be that self.list does not retain the array, and when filling the table view you add references to the strings in that list. Your property should look like;

@property (retain) NSArray* list;

This is not a problem in the first example because the strings are literal - e.g. they are embedded in your program and are never deallocated.

The second example creates a temporary string, and although its reference is incremented when added to the array it will later deallocated and destroyed when the array is released.

Also this code;

NSString *fieldName = [[NSString alloc] init];
fieldName = [NSString stringWithFormat:@"%@",@"Ligne1"];

Is going to result in a memory leak. You are allocating a new string, then changing the value in the pointer to be the result of the stringWithFormat call. If you wish fieldname to persist then the correct code would be;

NSString *fieldName = [[NSString stringWithFormat:@"%@",@"Ligne1"] retain];

Upvotes: 2

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