What is the best way to store data in an objective-c model?

I am writing an objective-c model to hold all of the data parsed from an XML connection. I am using an NSURLConnection to download the data asynchronously and it is then passed to the parser. I have done this before, but not with such a large xml file. I would like to garner some opinions on the best way to store the data. Here are some options:

1. Create a bunch of NSMutableDictionary's that represent the sections in the xml. Then add a key/value to these dictionaries with the child tags.

2. Create structs to hold the data as such:

   `struct section_one { NSString *string1; NSString *string2; } sectionOne;

The only thing I'm worried about is how to go about m开发者_开发知识库anaging the memory of the strings inside the struct. Should I copy the strings when I am instantiating them and release each individual string in the dealloc of the Model class.

Overall, I would just like some suggestions as to how to store the data.

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I'd suggest using NSDictionary instances nested inside another NSDictionary (whether these need to mutable or not depends on how you intend to use them, so I won't comment on that). The keys to the top-level dictionary could then be sectionOne, sectionTwo, etc., and their corresponding values would be the nested dictionary instances.