snippet from DebugTableViewController to collect .log files and zip them into an email attachment.

DebugViewController.m

#import "DebugTableViewController.h"
#import <ZipArchive/ZipArchive.h>
#import <MessageUI/MessageUI.h>


@interface DebugTableViewController ()<MFMailComposeViewControllerDelegate>

@end

@implementation DebugTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];
  
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


- (void)showAlertWithTitle: (NSString*)title message: (NSString*)message {
    UIAlertController* alert = [UIAlertController alertControllerWithTitle:title
                                                                   message:message
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
                                                          handler:^(UIAlertAction * action) {
                                                              [alert dismissViewControllerAnimated:YES completion:nil];
                                                          }];
    [alert addAction:defaultAction];
    
    [self presentViewController:alert animated:YES completion:nil];
    
}

- (NSString *)cachesDirectory {
    
    return NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
}

- (NSString *)logsDirectory {
    
    return [[self cachesDirectory] stringByAppendingPathComponent:@"Logs"];
}

- (NSData *)zipLogs {
    
    NSString *logsDir = [self logsDirectory];
    NSArray *files = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:logsDir error:nil];
    NSPredicate *textFilePredicate = [NSPredicate predicateWithFormat:@"self ENDSWITH '.log'"];
    files = [files filteredArrayUsingPredicate:textFilePredicate];
    
    NSString *logZipPath = [logsDir stringByAppendingPathComponent:@"logs.zip"];
    if ([[NSFileManager defaultManager] fileExistsAtPath:logZipPath]) {
        [[NSFileManager defaultManager] removeItemAtPath:logZipPath error:nil];
    }
    
    
    ZipArchive *za = [[ZipArchive alloc] initWithFileManager:[NSFileManager defaultManager]];
    
    [za CreateZipFile2:logZipPath];
    
    for (NSString *file in files) {
        DDLogVerbose(@"Log File being added to zip %@", file);
        [za addFileToZip:[logsDir stringByAppendingPathComponent:file] newname:file];
    }
    
    [za CloseZipFile2];
    
    NSData *zipData = [NSData dataWithContentsOfFile:logZipPath];
    [[NSFileManager defaultManager] removeItemAtPath:logZipPath error:nil];
    return zipData;

    
}
- (IBAction)emailLogFiles:(id)sender {
    
    NSLog(@"email log files");

    if (![MFMailComposeViewController canSendMail]) {
        [self showAlertWithTitle:@"Unable to email log files" message:@"Please make sure email is setup on your device."];
        return;
    }
    
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{
        NSData *zipFileData = [self zipLogs];
        
        dispatch_async(dispatch_get_main_queue(), ^{
            MFMailComposeViewController *mailVC = [[MFMailComposeViewController alloc] init];
            [mailVC setSubject:@"Application Log Files"];
            [mailVC setToRecipients:@[@"youremail.com"]];
            [mailVC setMessageBody:@"Please find the attached logs" isHTML:NO];
            
            [mailVC addAttachmentData:zipFileData
                             mimeType:@"application/zip"
                             fileName:@"logs.zip"];
            
            [mailVC setMailComposeDelegate:self];
            
            [self presentViewController:mailVC animated:YES completion:nil];
        });
    });
    
}

- (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error {
    switch (result) {
        case MFMailComposeResultSaved:
            DDLogInfo(@"Saved as a draft");
            break;
            
        case MFMailComposeResultCancelled:
            DDLogInfo(@"Mail cancelled");
            break;
            
        case MFMailComposeResultSent:
            DDLogInfo(@"Mail sent");
            break;
            
        case MFMailComposeResultFailed:
            DDLogInfo(@"Mail send failed");
            break;
    }
    
    if (error) {
        DDLogError(@"Error sending log files %@",error);
    }
    
    [self dismissViewControllerAnimated:YES completion:nil];
}




@end