set back button.m

    UIButton *backButton = [[UIButton alloc] init];
    [backButton addTarget:self action:@selector(backButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
    
    backButton.titleLabel.font = [UIFont fontWithName:@"ivvi-app-thumbnav-icons" size:34];
    [backButton setTitle:@"\ue820" forState:UIControlStateNormal];
    [backButton setTitleColor:[UIColor ivviNavigationTitle] forState:UIControlStateNormal];

    CGFloat leftInset = [self.navigationController.navigationBar respondsToSelector:@selector(layoutMargins)] ? 14 : 10;
    backButton.frame = CGRectMake(0, 0.0f, 44.0f, 44.0f);
    backButton.contentEdgeInsets = UIEdgeInsetsMake(0, -leftInset, 0, 20);
    [backButton setContentHorizontalAlignment:UIControlContentHorizontalAlignmentLeft];
    UIView * view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 60.0f, 44.0f)];
    view.userInteractionEnabled = YES;
    [view addSubview:backButton];
    
    UIBarButtonItem *customBarItem = [[UIBarButtonItem alloc]initWithCustomView:backButton];
    self.navigationItem.leftBarButtonItem = customBarItem;