Question

I made some codes to count every parenthesis from some string,

Is there any simpler way?

NSCharacterSet *parenthesis = [NSCharacterSet characterSetWithCharactersInString:@"()"];
parenthesis = [parenthesis invertedSet];
NSArray *arr = [someString componentsSeparatedByCharactersInSet:parenthesis];
NSInteger count = 0;
for(int i=0;i<[arr count];i++)  {
    if([[arr objectAtIndex:i] isEqualToString:@")"])
        count++;
}
NSLog(@"count is %d", count);

Answer 1

Since you need to walk through all characters in the string anyway, why not simply

NSUInteger count = 0;
for (NSInteger i = someString.length - 1 ; i >= 0 ; i--) {
    unichar ch = [someString characterAtIndex:i];
    count += (ch == '(' || ch == ')');
}

This uses fewer classes, much easier to read, and uses less CPU to perform the calculations.