Question

In addAlarm Controller, I am declaring an NSString as below,

   NSString *nameOfAlarm; // in .h

  @property (nonatomic, retain) NSString *nameOfAlarm; //in .h

  @synthesize nameOfAlarm; //in .m

and In ViewDidLoad, I am initializing it as following

  nameOfAlarm = [[NSString alloc] initWithString:@"Alarm"];//In ViewDidLoad

then after I am doing something like below

    // Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 
NSString *CellIdentifier = [NSString stringWithFormat:@"Cell%d%d", indexPath.section, indexPath.row];

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];
}

[cell setSelectionStyle:UITableViewCellSelectionStyleNone];
   // Configure the cell...

if (indexPath.section == 0) {
    UISwitch *mySwitch = [[[UISwitch alloc] initWithFrame:CGRectZero] autorelease];
    cell.accessoryView = mySwitch;
    [(UISwitch *)cell.accessoryView setOn:YES];   // Or NO, obviously!
    [(UISwitch *)cell.accessoryView addTarget:self action:@selector(mySelector:)
                             forControlEvents:UIControlEventValueChanged];
    NSString *cellValue = [NSString stringWithFormat:@"Enable Alarm"];
    cell.textLabel.text = cellValue;
    //return cell;      
}
if (indexPath.section == 1) {
    if (indexPath.row == 0) {
        NSString *cellValue = [NSString stringWithFormat:@"Name "];
        cell.textLabel.text = cellValue;

        NSString *cellValue2 = [NSString stringWithFormat:@"%@",(NSString*)nameOfAlarm];
        cell.detailTextLabel.text = cellValue2;

    }

so I am doing reload table in ViewWillAppear as below

- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
NSLog(@"ViewWillAppear, The name is  %@",nameOfAlarm);
[self.tableView reloadData];
 }

I am writing delegate method which is being called by other controller as followed,

- (void) processName: (NSString *)n{
nameOfAlarm = (NSString *)n;
NSLog(@"Name is %@",nameOfAlarm);
}

Now when I click on 0 index of row, it will go to Name controller, simply, the .h of name controller is

#import <UIKit/UIKit.h>

@protocol ProcessNameDelegate <NSObject>
@required
- (void) processName: (NSString *)n;
@end

@interface Name : UITableViewController <UITextFieldDelegate>{

id <ProcessNameDelegate> delegate;
    UITextField *name_textField;
}

@property (retain) id delegate;
@property (nonatomic, retain) UITextField *name_textField;

- (void)pressComplete;

@end

and when pop back to previous controller, then will call the following method is ViewWillDisappear,

- (void)pressComplete {
    NSString *name = (NSString *)name_textField.text;
[[self delegate] processName:name];
}

This will set value to nameOfAlarm
Everything is fine, but when I do reload then this is not showing in

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

It is showing something like below if I do use nameOfAlarm in cell value or even just doing NSLog,

    <_UIStretchableImage: 0x14db10> //the first time in nameOfAlarm,

the second time If I will go in Name controller and do it, then will print as follows

<UILabel: 0x1cd6c0; frame = (13 0; 25 27); text = 'ON'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x1d75f0>>

or like this

<UILabel: 0x179ed0; frame = (101 0; 32 27); text = 'OFF'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x179f40>>

I am not able to get the problem, because the same variable is working showing correct values in other methods, but not working well with

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

Why?

Answer 1

In processName: you do this:

nameOfAlarm = (NSString *)n;

The cast is not necessary but it doesn’t hurt. The problem is that you are not retaining n and it can go away any minute leaving you with a dangling pointer. You need to do this:

self.nameOfAlarm = n; // which is different from nameOfAlarm = n;

The dot notation is just syntactic sugar for:

[self setNameOfAlarm:n];

Since the property is marked retain, the property setter that is created for you via synthesize will retain the new value of nameOfAlarm (n) and release the old value of nameOfAlarm.