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    <p>Now that you have described haw you want to represent the various data, before defining the complete relations, try to complete the description by defining the "<em>protocols</em>":</p> <p>What can each class be able to do to the others? WHat methods and rules between methods are needed to achieve your goal?</p> <p>Once you have defined how classes act on each other you will most likely discover what is candidate to be private, what is public and what level of friendship must exist between the parties.</p> <p>May be is not your case, but -usually- when complex relations exist, one possible pattern can be the use of a "communication bus class", that expose the action that can be "sent" to the various object, each having a private interface and being friend of ... the bus itself (an only the bus).</p> <p><strong>EDIT</strong></p> <p>Following Svalorzen comment:</p> <p>It depends on the side you are watching it. This will, in fact, introduce multiple level of "privacy", allowing to implement encapsulation on a wider unit that the class itself. Whether this is good or bad is a matter of context, not idiom.</p> <p>Instead of having just classes with everything private (for no-one else) or public (for anyone), you have a "<em>capsule</em>" that is a "club" (the "club of the classes having 'bus' as a friend") and a "club manager" the is the real "filter towards the public" (and hence the real OOP object), allowing certain methods that need to interact with more classes private parts at a same time, to do that inside the club only.</p> <p>The deny of "friendship" is nothing more than a misconception that confuse techniques with tools, making OOP objects the same as C++ classes. That's -generally speaking- a FASLE IDIOM. C++ classes can be smaller units than OOP objects (think to the <em>pimpl</em> idiom: what is the "object" there?). The fact that a class can be a friend of another doesn't make it a friend of anyone, hence the private parts are not made public. You are just defining another level of privacy where encapsulation apply the same as with "private". It just apply on a wider group. That "wider group" plays, respect to OOP, the same role a non-friend class plays.</p> <p>The misconception that "friend breaks encapsulation" has nothing to do with the concept of OOP. It has to do with the way OOP has been implemented in Java, that is a completely different language respect to C++. In C++ friendsip is just a construct to "group thimgs together" just like class, struct, templates, inheritance, membership etc.</p> <p>What OOP relation (composition, inheritance, linking...) has to be mapped to what C++ construct, unlike in java, when the language philosophy is defined to be one-way only, is not defined by the language itself and by it's standard library.</p> <p>The mapping "OOP object = C++ class" is just a common cultural misconception inherited from the past, when C++ has no templates, no lambdas, no friendship, nothing more than classes (and was in fact called "C with classes") when the only way to implement an OOP hierarchy was through classes,since that was the only way to create a hierarchy relation using that time c++ constructs.</p> <p>Nowadays I can even implement an OOP system using C++ members and implicit conversion for "OOP inheritance" and C++ private inheritance for "OOP membership". Or I can implement an OOP object with a "cluster of classes (or mat be labdas)", defining its run-time behavior (think to std::locale and related facets).</p> <p>Starting a design with the OOP object == C++ classes idioms is in fact cutting away two degrees of freedom C++ adds to program design, restricting your mind to what C++ was more than ten years ago.</p>
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    1. POWhat is the best way to arrange this classes?
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    1. USEmilio Garavaglia
    1. USEmilio Garavaglia
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    1. COHow would the bus class be implemented? I mean, if every class had to send its own actions to this class, it would have to have access to everything. Wouldn't this be as bad as simply cutting away layers and grouping stuff in big clumps?
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    2. CO@Svalorzen: see my edit
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