Have you ever wanted to open the Mail app with a pre-composed email? Then today’s iPhone development advent tip is the one for you! This has many uses, but a common one is a tell-a-friend feature in apps. If you attach the code from this tip to a button, you can give your users a way to promote your app to their friends via the iPhone’s built in Mail app.

A Handy Function

The sendEmailTo function, seen below, can be included in any class in your app. This function gives you a simple interface to send emails. It allows you to define “to” addresses, “cc” addresses, “bcc” addresses, a subject and a body. The body supports HTML tags.

- (void)sendEmailTo:(NSString*)to withCC:(NSString*)cc withBCC:(NSString*)bcc withSubject:(NSString*)subject withBody:(NSString*)body {
	NSString * url = [NSString stringWithFormat:@"mailto:?to=%@&cc=%@&bcc=%@&subject=%@&body=%@",
					  [to stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
					  [cc stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
					  [bcc stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
					  [subject stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding],
					  [body stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]];
 
	[[UIApplication sharedApplication] openURL:[NSURL URLWithString:url]];
}

NOTE: Running this function in the iPhone Simulator will have no effect because the simulator does not include the iPhone’s Mail app. To see the effects of this function, it must be run on a device.

Example Usage

Once you have that message defined in one of your classes, you can open the Mail app with a pre-composed email with just one message call. The following example opens an email and specifies a to, cc and bcc address. It populates the subject with “Addicus” and populates the body with a short message about Addicus that includes a link and an image (which is also a link). As you can see, this is done with good old HTML tags. This results in the email in the above screenshot.

[self sendEmailTo:@"mom@example.com"
           withCC:@"dad@example.com"
          withBCC:@"asecretfriend@example.com"
      withSubject:@"Addicus"
         withBody:@"<p>Check out this game, <a href='http://addicusgame.com'>Addicus</a>, for the iPhone and iPod Touch. It's super-addictive!</p><p><a href='http://addicusgame.com'><img src='http://getsetgames.com/wp-content/uploads/2009/11/icon_addicus.png'/></a></p>"];

If you would like to have the user specify the to, cc and bcc addresses themselves, as you would in the case of a tell-a-friend button, then you would call the following message:

[self sendEmailTo:@""
           withCC:@""
          withBCC:@""
      withSubject:@"Addicus"
         withBody:@"<p>Check out this game, <a href='http://addicusgame.com'>Addicus</a>, for the iPhone and iPod Touch. It's super-addictive!</p><p><a href='http://addicusgame.com'><img src='http://getsetgames.com/wp-content/uploads/2009/11/icon_addicus.png'/></a></p>"];

Ever have the need to call a method inside your app delegate from an arbitrary place in your code?  We’ve had to deal with this issue in a few cases working on our new project.  We’re making use of a UIScrollView instance to give us that popular flick scroll movement that is so popular on the iPhone.  We’ve found that alot of people have been interested in doing the same thing and you can read our blog on that particular challenge here.  We have a UIScrollView instance sitting inside our app delegate and there are certain parts of our code where we need to move that UIScrollView among different layers in Cocos 2D.  To do that we need access to the scroll view instance itself.  That results in code like the following…

myAppDelegate *app = [[UIApplication sharedApplication] delegate];
UIScrollView *appOverlayScrollView  = (UIScrollView *)app.view;
[[app window] sendSubviewToBack:appOverlayScrollView];

This creates a messy dependency between an arbitrary class and the app delegate class.  Wouldn’t it be great if we could send a message to the app delegate and tell it to move the scroll view to the front or back maintaining encapsulation?  Turns out you can indeed do this.  The UIApplication class contains a method called sendAction which is normally used to send an action message identified by a selector to a specified target.  This method can easily be used to call selectors in any object so the above code can be converted to…

[[UIApplication sharedApplication]
sendAction:@selector(bringScrollViewToFront)
to:[[UIApplication sharedApplication] delegate]
from:self
forEvent:nil];

The only downside to this approach is that I haven’t found a way to supply arguments along with the selector so you need to be calling a method with no arguments.  If you know of a way around this issue please do let me know.

Tis the season to broaden your iPhone dev chops! We have been developing on the iPhone platform for about 6 months now and it turns out that in that time, you tend to learn lots of little tips and tricks. Since we’re overcome by the spirit of giving around this time of year, we are going to be posting 24 of these bite-sized iPhone development tips, 1 every day between now and Christmas day. Consider it an advent calendar of iPhone dev tip goodies.

On With The First Tip!

Say you would like to open a URL in Safari. We used this on the “Get Set” button on the main menu of Addicus. Here is how to do it with just one line of code using the UIApplication class:

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://getsetgames.com/"]];