Create an entity class

How can I create an entity class in an iPhone project? Please give me a very simple example, because I'm new in iPhone development.

@Edit:: So create a Base-entity containing the properties which will be common for all the classes, then create the Observable-class and make it inherit from the Base-class. In this app we might very well be able to use the Observable as a base class for the other entities because an Observable should be able to be saves as a Dialogue for example开发者_StackOverflow中文版.

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Here are a very simple tutorials, check links bellow:

• iPhone Development and a sample Objective C Program
• Tutorial: Creating Class Categories in Objective C