Variable losing its value (iPhone SDK)

Question

I declare a variable in the header file and synthesize it in the implementation. When the view loads (ViewDidLoad) I read a plist file an populate the variable with a value. WIth my NSLog I see that the variable contains the value. However, after the view loads, I have some interaction with the user via a button the executes a method. WIthin that method I check the value again and it is invalid. Why won't the variable maintain its value after the initial load?

program.h

....
NSString * user_title;
...
@property (nonatomic, retain) NSString *user_title;

program.m

@synthesize user_title;

-(void)viewDidLoad{

    NSString *filePath = [self dataFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath])
{
 NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
 user_title = [array objectAtIndex:0];
 [array release];
}
    ....


-(IBAction)user_touch_screen:(id)sender
 {
    user_label.text = user_title;  //user_title has an invaliud value at this point
   ....

Answer 1

You need to retain the value you get out of the array.

Answer 2

user_title = [array objectAtIndex:0] doesn't retain the variable.

Use this instead:

self.user_title = [array objectAtIndex:0];

That will use the setter that you synthesized, and will retain the value.