Sum all the file size under a given folder path

NSFileManager+UUFileSizeCalculations.h

#import <Foundation/Foundation.h>

@interface NSFileManager (UUFileSizeCalculations)

- (unsigned long long) uuFileSizeAtPath:(NSString*)path;

@end

NSFileManager+UUFileSizeCalculations.m

#import "NSFileManager+UUFileSizeCalculations.h"

@implementation NSFileManager (UUFileSizeCalculations)

- (unsigned long long) uuFileSizeAtPath:(NSString*)path
{
    unsigned long long totalSize = 0;
    
    BOOL isDir;
    if ([self fileExistsAtPath:path isDirectory:&isDir])
    {
        if (isDir)
        {
            NSError* err = nil;
            NSArray* list = [self subpathsOfDirectoryAtPath:path error:&err];
            if (!err && list)
            {
                for (NSString* subPath in list)
                {
                    NSString* fullSubPath = [path stringByAppendingPathComponent:subPath];
                    
                    err = nil;
                    NSDictionary* attrs = [self attributesOfItemAtPath:fullSubPath error:&err];
                    if (!err && attrs)
                    {
                        NSNumber* fileSize = [attrs valueForKey:NSFileSize];
                        if (fileSize)
                        {
                            totalSize += fileSize.unsignedLongLongValue;
                        }
                    }
                }
            }
        }
    }
    
    return totalSize;
}

@end