Recipe: Using Instruments to Monitor Cached Object Allocations

When you load too much data at once, you can also run short of memory. Holding onto everything in your program when you are using memory-intense resources such as images, audio, or PDFs may cause problems. A strategy called caching lets you delay loads until resources are actually needed and release that memory when the system needs it.

The simplest approach involves building a cache from an NSMutableDictionary object. A basic object cache works like this: When queried, the cache checks to see whether the requested object has already been loaded. If it has not, the cache sends out a load request based on the object name. The object load method might retrieve data locally or from the Web. After the data is loaded, the cache stores the new information in memory for quick recall.