如何在IOS的反馈表单上自动填充电子邮件地址？

picker.mailComposeDelegate = self;
NSArray *toRecipients = [NSArray arrayWithObject:@"abcd@xyz.com"];
NSString *tosubject =txtSubject.text;
[picker setSubject:tosubject];


// Set up recipients
[picker setToRecipients:toRecipients];