CODEWITHSUNDEEP
c++
trikker
trikker

Reputation: 2719

Where to put containers of user defined types?

Consider one has some user defined types, and containers of those types that are often manipulated because there are often multiple instances of those types on screen at a time.

Currently I have a header with an associated source file and a namespace to hold these containers, but should I create a separate class to hold them? Should I put the containers in the same header file as the class that they contain (but obviously outside the class)? What is the standard practice for situations like this?

Upvotes: 1

Views: 137

Answers (1)

Doug T.
Doug T.

Reputation: 65649

I once typedef'd them whenever a specific class has the container as part of that class's interface. Then anyone who needed to use that class easily figured out that a "FooVec" is a std::vector of Foo without a lot of fus.

However, this is an imperfect solution, consider the following code:

namespace bar
{

  typedef std::vector<Foo> FooVec;

  class CClass
  {
      CClass(FooVec&)
      {
          ...
      }
  };
}

Naturally the problem comes in when your colleague redefines FooVec for their class:

namespace bar
{

typedef std::vector<const Foo> FooVec;

class CAnotherClass
{
    CAnotherClass(FooVec&)
    {
        ...
    }
}

};

The simplest thing I've found to solve this is to have them in roughly one common include per namespace/library/group of associated classes. So when someone else adds a typedef to something in the bar namespace, you can have them all in one place. IE:

 barTypes.h

 namespace bar
 {
         typedef std::vector<Foo> FooVec;
         typedef std::vector<const Foo> FooConstVec;

 }

By keeping it to one header per small set of classes (ie per namespace) you don't get a gigantic file full of typedefs. It still gives your users good visibility into the types that are a part of your class's interface. Once this header is established, its just a matter of maintaining discipline on your team to use it instead of establishing additional typedefs.

May also wish to have this header as part of a precompiled header if you're anal about build performance.

Upvotes: 2

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