Question

I have a method called getProjects. In my method I parse data from json. I save name and id of the project in my instance variable projectsArray which is an NSMutableArray.

The problem is that I have a button (IBAction) called writeFile and if I try to log the array on click, my app crashes. The error message is ESC_BAD_ACCESS. But why? I am using ARC.
`Method getProjects

- (void)getProjects {
int count = 0;
self.projectsArray      = [NSMutableArray arrayWithCapacity:10];
SBJsonParser *parser    = [[SBJsonParser alloc] init];

NSURLRequest *request   = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"[e-mail]", urlPath]]];
NSData *response        = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

NSString *json_string   = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];
NSArray *projects       = [parser objectWithString:json_string error:nil];

for (NSDictionary *project in projects) {
    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:2];

    [dict setObject:[project objectForKey:@"name"] forKey:@"name"];
    [dict setObject:[project objectForKey:@"id"] forKey:@"id"];

    [self.projectsArray insertObject:dict atIndex:count];
    [self.selectProject addItemWithTitle:[project objectForKey:@"name"]];
    count++;
}

}

And I call the method in applicationDidFinishLaunching

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    [self getProjects];
    NSLog(@"%@", self.projectsArray);
}

The log in my applicationDidFinishLaunching returns my array.

Answer 1

Well, it seems you have already found the cause of the issue:

I changed assign to retain and now it works. But why?

The reason is that by declaring the property as assign, when you set it, its value is not retained.

So:

1. you create the array like this:

     self.projectsArray      = [NSMutableArray arrayWithCapacity:10];
   

2. arraywithCapacity will give you an autoreleased object;

3. the object is not retain when assigning it to the property;

4. at some point in time, before the NSLog is executed, the object is deallocated.

5. crash.