Why does my MFMailComposeViewController instance only dismiss one time? - ios

Question

I'm trying to track down the source of a bug in a cordova/phonegap plugin I wrote for creating email messages in app using a MFMailComposeViewController instance.
Everyone works fine the first time you present the the composer view. The user can dismiss the mail composer by sending the message or canceling. However, call presentViewController again renders the Cancel and Send buttons in the composer to become useless. My delegate for didFinishWithResult is never calling when pressing the inoperable buttons with the second view of the controller.
Below is simplified repro of what I'm seeing (the simple storyboard has a single view containing a single UIButton wired to my (IBAction)sendMail). What am I doing wrong in obj-c here? Shouldn't I be able to show a controller, dismiss it, and show it again?
ViewController.h:
#import <UIKit/UIKit.h>
#import <MessageUI/MessageUI.h>
#interface ViewController : UIViewController
#end
ViewController.m:
#import "ViewController.h"
#interface ViewController () <MFMailComposeViewControllerDelegate>
#property (nonatomic, weak) IBOutlet UIButton *mailButton;
#property(nonatomic, strong) MFMailComposeViewController* picker;
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.picker = [[MFMailComposeViewController alloc] init];
self.picker.mailComposeDelegate = self;
}
- (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error
{
[self dismissViewControllerAnimated:YES completion:NULL];
}
- (IBAction)sendMail
{
[self presentViewController:self.picker animated:YES completion:NULL];
}
#end

Answer 1

The reason for the behavior you are experiencing is the MFMailComposeViewController nils it's delegate when dismissed (maybe in -viewDidDisappear:).
- (void)viewDidLoad
{
[super viewDidLoad];
self.picker = [[MFMailComposeViewController alloc] init];
self.picker.mailComposeDelegate = self;
}
- (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error
{
// Put a break point here **#breakpoint1**
[self dismissViewControllerAnimated:YES completion:NULL];
}
- (IBAction)sendMail
{
// Put a break point here **#breakpoint2**
[self presentViewController:self.picker animated:YES completion:NULL];
}
Place breakpoints at shown in the code comment above, run, and follow me as we step through your code.
Tap the interface button that calls your IBAction; execution halts at #breakpoint2
In the console type po self.picker
You'll see the mail compose VC instance is allocated
In the console type po self and then po self.picker.delegate
You'll see these both print the same object (the instance of your view controller)
Resume running, and tap the dismiss button on the mail compose view; execution halts at #breakpoint1
If you want to, inspect local and instance variables in console and then resume running
Tap the interface button that calls your IBAction (this is the second time); execution halts at #breakpoint2
In the console typ po self.picker.delegate
nil is printed to console
This delegate nil'ing behavior isn't documented in either Apple's MFMailComposeViewController class reference or the classes header. It's probably worth filing a bug report requesting clarification and better documentation. Because it's undocumented, the behavior may change in future releases. For that reason, the suggestions to create and destroy the VC as needed certainly seem like good common sense.

Answer 2

This bit me once before. It's caused by the composer being deallocated after it's done being dismissed. To solve this I would place the composer's creation either in viewDidAppear:, or in sendMail as Fahim suggested.
Additionally, you may want to consider wrapping these two lines in [MFMailComposeViewController canSendMail];

Answer 3

I would say take below lines to sendMail... it would work.
self.picker = [[MFMailComposeViewController alloc] init];
self.picker.mailComposeDelegate = self;
You will have as below.
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (IBAction)sendMail
{
self.picker = [[MFMailComposeViewController alloc] init];
self.picker.mailComposeDelegate = self;
[self presentViewController:self.picker animated:YES completion:NULL];
}
#end
This is working with me...