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POHow to associate calculated values to an object
 

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  1. POHow to associate calculated values to an object
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    <p>I have some basic objects like Customer, Portfolio and ... with some association to other objects. I can easily display the required information in the web page by reading object values. The problem is that what do I do when the value associated with the object is calculated and returned by a method, a value that makes sense only in certain context and cannot be attached to the object as an instance variable? In this case if I have a list of say Users I have to pass the username of each user to the method to get the calculated value. This causes problem to keep the association while displaying the values in the page. </p> <p><strong>An example to make this clear:</strong><br> An application provides the functionality for users to keep track of each others activities by letting them add whoever they want to a list. If this user performs a search on users there's the option to follow each returned user. I want to make sure this option is disabled for those user's that are already being followed. This functionality is provided by a method like <code>isFollowed(String follower, String followee)</code> which returnes a boolean. How can I associate this boolean values to each user in search result? </p> <p><strong>Solutions:</strong><br> One thing I can think of is to add a <code>followed</code> instance variable to User class. But I don't think it's a good approach because this variable only makes sense in a certain context. It's not a part of User class in the domain.<br> The other way I can think of is to use <em>Decoration</em> or <em>Wrappers</em> in a way to extend the User class and add the attribute in the child class. But again what if I have several objects that need to be in the same context. In that case I have to extend all of them with the same boolean attribute in all classes.</p> <p>I hope I could make it clear.</p>
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    1. COI'm not finding the question very clear, sorry - could you provide some more concrete example of the context?
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      1. USThe Evil Greebo
 

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