Question

I was surprised to see in a objective-c project, the following line codes

- (void)methodName
{
    ... some code...

    {
        ... some code
    }

    {
        ... some code
    }

}

What does the inner brackets stand for ? They seems not be preceded by any statement.
thanks

Answer 1

The brackets create a new scope. Variables defined within the scope will not persist after the end of the scope. I personally use this to separate out bits of logic to make things easier to read.

Example 1

This example demonstrates the lack of access to variables instantiated inside of a more narrowly defined scope.

-(void)blockTestA {
    int j = 25;

    {
        int k = 5;

        // You can access both variables 'j' and 'k' inside this block.
    }

    // You can only access the variable 'j' here.
}

Example 2

This example demonstrates how creating a new block scope allows us to have different variables with the same name. You can read more about scope here.

-(void)blockTestB {
    int j = 25;

    {
        int j = 5;
        NSLog(@"j inside block is: %i", j); // Prints '5'
    }

    NSLog(@"j outside of block is: %i", j); // Prints '25'
}