Dynamic link in IOS 3 with IOS 4 library

I have to make an app that draw circles in a map, I made it using MKOverlay , the problem is that MKOverlay is available from IOS 4 and my app should be install in IOS 3.1 . I can accept don`t draw circle开发者_开发问答s if the app run in IOS 3 , but if the app is runing on device with IOS 4 cricles must be draw in the map.

I put IF_IOS4_OR_GREATER in the code to dif between IOS 3 and IOS 4, that works great, but in some part I have that

import MapKit/MKOverlay.h <---- Problem

@interface Circle : MKCircle { <----- Problem "MkCircle" (not available ... ... } so I have a compile time error (because I compile that for IOS 3). What is the best way to solve this problem?

Thanks and excuse me for my horrible english :s

Set your Base SDK to 4.2 and your compiler to LLVM GCC. Basically, do everything as Marco Arment described in this blog post: http://www.marco.org/1648550153