CODEWITHSUNDEEP
c++code-organization
rossb83
rossb83

Reputation: 1762

Organizing large C++ project

Should all C++ code in a project be encapsulated into a single class with main simply calling that class? Or should the main function declare variables and classes.

Upvotes: 3

Views: 9539

Answers (6)

Brian Kelly
Brian Kelly

Reputation: 19305

If you are going to build a large project in C++, you should at the very least read Large Scale C++ Software Design by John Lakos about it. It's a little old but it sounds like you could benefit from the fundamentals in it.

Keep in mind that building a large scale system in any language is a challenge and requires skill and discipline to prevent it falling to pieces very quickly. Don't take it lightly.

That said, if your definition of "large" is different than mine then I may have alternative advice to give you. I'm assuming you're talking about a project where the word "million" will be mentioned in sentences that also contain the words "lines of code".

Upvotes: 11

iammilind
iammilind

Reputation: 70094

In C++ you should avoid putting entire project in one class, irrespective of big or small. At the max you can try putting it in 1 or 2 namespace (which can be split across the files). The advantage of having multiple classes are,

  1. Better maintainability of your code
  2. Putting classes in multiple .h and .cpp files (i.e. small modules) help you fast debugging
  3. If all code is in one class and changes are made somewhere then one has to compile whole project. Instead, if project is across modules, one can just compile the module where changes are made. It saves time a lot.

Upvotes: 1

Mike Kale
Mike Kale

Reputation: 4133

If you can put your entire project in one class without going insane, your definition of "large" may be different than most people's here. Which is fine -- just keep in mind when you ask people about a "large" c++ project, they will assume you're talking about something that takes multiple person-years to create.

That said, the same principles of encapsulation apply no matter what the size of the project. Break your logic and data into units that make sense and are not too tied together and then organize your class(es) around those divisions. Don't be afraid to try one organization and then refactor it into another organization if you find yourself copy-pasting code, or if you find one class depending too heavily on another. (Or if you find yourself with too many classes and you're creating many objects to accomplish one task where a single object would be cleaner and easier on you.)

Have fun and don't be afraid to experiment a little.

Upvotes: 1

Jerry Coffin
Jerry Coffin

Reputation: 490758

If it's a class that really makes sense, sure -- but at least IME, that's a fairly rare exception, not the general rule.

Here, I'm presuming that you don't really mean all the code is in one class, but that there's a single top-level class, so essentially all main does is instantiate and use it. That class, in turn, will presumably instantiate and use other subordinate classes.

If you really mean "should all the code being contained in a single class?", then the answer is almost certainly a resounding "no", except for truly minuscule projects. Much of the design of classes in C++ (and most other OO languages) is completely pointless if all the code is in one class.

Upvotes: 1

nahano
nahano

Reputation: 3835

No! Each header/implementation file pair should represent a single class. Placing a large project in one file is a surefire way to disaster: the project become unmaintainable and compiling will take ages. Break up your code in to appropriately sized pieces.

The main function should not declare the classes, rather, the file it contains (often named something like main.cpp, driver.cpp, projectname.cpp) should use #include directives to make the compiler read the declarations in header files. Read up on C++'s separate compilation model for more info.

Some newcomers to C++ find the compilation model - as well as error codes generated when you screw it up - incomprehensible or intimidating and give up thinking it's not worth it. Don't let this be you. Learn how to properly organize your code.

Upvotes: 0

Keith Nicholas
Keith Nicholas

Reputation: 44316

for large C++ projects, you should create many classes!

main should just kick things off (maybe doing a few housekeeping things) and then calling into a class that will fire up the rest of the system

Upvotes: 1

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