How to implement didReceiveMemoryWarning?

Question

I have developed a simple location aware iPhone application which is functionally working very well to our expectations except in the low memory condition of the phone .

Answer 1

Memory warnings are a signal to you that you should dispose of any resources which aren't absolutely critical. Most of your controllers will be hanging onto data caches, intermediary data, or other bits and pieces, often to save recalculation. When they receive memory warnings, they should begin flushing anything they don't immediately need in order to operate.

How you determine what is "critical" depends entirely on your application's design. An OpenGL game, for example, may determine that textures currently on-screen are valuable and flush textures which aren't visible, or level data which is outside the bounds of the current play area. An application with extensive session logs (like an IRC client) may flush them out of memory and onto disk.

As you observed, the warning is sent to each controller in your hierarchy, so each piece needs to determine individually what data constitutes "critical for operation" and what constitutes "expendable". If you've optimized them all and are still getting out of memory warnings, it's unfortunately time to revisit your core application design, because you're exceeding the limits of the hardware.