I am trying to configure it so that people can send messages from my application. I refer to this post to do this, but I get these warnings in the assembly: 
and then when I started it, it mistakenly: 
I am wondering if I just put the code in the wrong place. Just so you know what I posted
#import <MessageUI/MessageUI.h>
in the header file.
Thanks for the help!
EDIT 1
It seems that the problem is how my ViewController is configured. In fact, all of my user interface code is in a separate object, as shown below. This makes it difficult for me to understand which code goes there. Any advice? 
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