Error while checking if a file exists

Question

Hi,

I'm trying to write to a plist file using writeToFile, before I write I check whether the file exists.

This is the code:

#import "WindowController.h"

@implementation WindowController

@synthesize contacts;

NSString *filePath;
NSFileManager *fileManager;

- (IBAction)addContactAction:(id)sender {

    NSDictionary *dict =[NSDictionary dictionaryWithObjectsAndKeys:
          [txtFirstName stringValue], @"firstName",
          [txtLastName stringValue], @"lastName",
          [txtPhoneNumber stringValue], @"phoneNumber",
          nil];

    [arrayContacts addObject:dict];

    [self updateFile];
}

- (void)awakeFromNib {
    NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    filePath    = [rootPath stringByAppendingPathComponent:@"Contacts.plist"];
    fileManager = [NSFileManager defaultManager];

    contacts = [[NSMutableArray alloc] init];

    if ([fileManager fileExistsAtPath:filePath]) {

     NSMutableArray *contactsFile = [[NSMutableArray alloc] initWithContentsOfFile:filePath];
     for (id contact in contactsFile) {
      [arrayContacts addObject:contact];
     }
    }
}

- (void) updateFile {
    if ( ![fileManager fileExistsAtPath:filePath] || [fileManager isWritableFileAtPath:filePath]) {
     [[arrayContacts arrangedObjects] writeToFile:filePath atomically:YES];
    }
}

@end

When the addContactAction is executed I don't get any error but the program halts and it brings me to the debugger. When I press continue in the debugger I get:

Program received signal:  “EXC_BAD_ACCESS”.

But that's probably not important.

PS: I'm new to mac programming and I don't know what else to try since I don't get an error message that tells me what's going wrong.

The path to the file is:

/Users/andre/Documents/Contacts.plist

I earlier tried this(with the same result), but I read that you can only write to the documents folder:

/Users/andre/Desktop/NN/NSTableView/build/Debug/NSTableView.app/Contents/Resources/Contacts.plist

Does anyone have an idea or even an explanation why this happens?

Answer 1

First, I think you shouldn't instantiate an NSFileManager object. Instead you use the default file manager, like this:

[[NSFileManager defaultManager] fileExistsAtPath: filePath];

Then, could you specify at which line the program is breaking into the debugger?

Answer 2

You are setting filePath with the stringByAppendingPathComponent: method. That method returns an autoreleased object. (Autoreleased object is used after it has been (automatically) released, which could cause the bad access error.)

I think changing

[rootPath stringByAppendingPathComponent:@"Contacts.plist"];

into

[[rootPath stringByAppendingPathComponent:@"Contacts.plist"] retain];

will solve your troubles.