What is happening if code is wrapped in curly braces within a function?

Question

I'm new to Objective C and have noticed in code I've read that sometimes a block of code will be wrapped in curly braces inside of a function.

What does this do?

For example ...

- (BOOL) application: (UIApplication *) application didFinishLaunchingWithOptions: (NSDictionary *) launchOptions {    

  // Load config, available via macro CONFIG
  {
    NSString *path = [[NSBundle mainBundle] pathForResource: @"config" ofType: @"plist"];
    NSData *data = [[NSData alloc] initWithContentsOfFile: path];
    self.config = [NSPropertyListSerialization propertyListWithData: data
                                                            options: NSPropertyListImmutable
                                                             format: nil
                                                              error: nil];
    [data release];
  }

  // snip

}

Answer 1

That's called "scope"...

Variables declared inside the braces only exists inside the braces.

Imagine the following:

int main( void )
{
  int my_var = 3;
  {
     int my_var = 5;
     printf( "my_var=%d\n", my_var );
  }

  printf( "my_var=%d\n", my_var );

  exit( 0 );
}

This will print:

my_var=5
my_var=3

Answer 2

It's just a way of limiting the scope of the variables declared in the block. In your example path and data will not be visible outside of the curly braces.