Re: [Boost-Users] Association Library?

From: hicks (hicks_at_[hidden])
Date: 2002-03-30 20:41:19

Hello

class RuntimeAssoc
{
std::map<Emp, Mgr>
std:::multimap<Mgr,Emp>
public:
insert(const Mgr&, const Emp&);
std::pair<Mgr, Emp> find(const Mgr&);
std::pair<Emp, Mgr> find(const Emp&);
};

I am not sure what you mean by "direct".  Do you mean compile time?
The STL provides an easy way to implement mutable associations at run 
time (as shown above);
There was an intersting article in C++ User's Journal last year 
containing an implemetation
of a many-to-many mapping class.

I think a "specific" example of what you want to do would be helpful.

Craig Hicks
KGK Ltd

rzako23 wrote:

>Are there any generic components in Boost (or elsewhere) for *directly* 
>representing associations between classes?
>
>Generalization, composition, aggregation and association are major 
>ideas in the object model. Generalization can be implemented fairly 
>directly in C++ using inheritance. Composition and aggregation can be 
>represented directly in C++ using data members (when the number of 
>parts in each whole is small and fixed), or using STL containers (when 
>the number of parts in each whole is large or variable). But Standard 
>C++ (including the STL) provides no *direct* support for representing 
>associations, i.e., collections of links between objects in two or more 
>classes. (David Papurt makes this point in "Inside the Object Model: 
>The Sensible Use of C++.")
>
>For example, the STL does not offer a way to *directly* represent the 
>1-to-many "Supervises" association from the Manager class to the 
>Employee class. One would like to have links in both directions: 
>forward links forthe employees a manager supervises and a back link to 
>the manager each employee is supervised by. Of course, one could code 
>this all "by hand" using a container of pointers to employees for each 
>manager and a back pointer for each employee. But the implementation 
>details really have little to do with managers and employees and would 
>be pretty much the same for parents and children or teachers and 
>students. Moreover, while not difficult, managing the forward and back 
>links correctly (and in an exception-safe manner) is tedious. It would 
>be nice to have templates that can be instantiated to implement 
>specific associations.
>
>In brief, STL containers directly support composition and aggregation 
>but not association.
>
>I am new to the Boost library, but was not able to find this capability 
>in Boost. If an association library is available in Boost (or 
>elsewhere), I would be happy to know so.
>
>If not, is an association library something that would be worth looking 
>into?
>
>Thanks,
>Rob Zako
>
>
>
>
>
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