NSString *extension = @"txt";
                NSFileManager *fileManager = [NSFileManager defaultManager];
                NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
                NSString *documentsDirectory = [paths objectAtIndex:0];
                
                NSArray *contents = [fileManager contentsOfDirectoryAtPath:documentsDirectory error:NULL];
                NSEnumerator *e = [contents objectEnumerator];
                NSString *filename;
                while ((filename = [e nextObject])) {
                    
                    if ([[filename pathExtension] isEqualToString:extension]||[[filename pathExtension] isEqualToString:@"db"]) {
                        
                        [fileManager removeItemAtPath:[documentsDirectory stringByAppendingPathComponent:filename] error:NULL];
                    }
                }
原文:http://www.cnblogs.com/isItOk/p/5866831.html