Programmatically control iPhone OS versions to enable functions for both OS 3.x and 4 - MFMessageComposeViewController problem

Question

In order to support iPhone OS 3.x and 4.0 I programmatically control MFMessageComposeViewController functionality like this (use it only if the OS version is 4.0 or above):

Answer 1

Class theClass = NSClassFromString(@"MFMessageComposeViewController");
MFMessageComposeViewController *controller = theClass ? [[theClass alloc] init] : nil;

You can use the type MFMessageComposeViewController as in:

MFMessageComposeViewController *controller;

But you cannot use the global object MFMessageComposeViewController as in:

[MFMessageComposeViewController alloc];

Instead use the class lookup so you are not dependent on the linker:

[NSClassFromString(@"MFMessageComposeViewController") alloc];