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Subject: [Boost-users] Unique parameter values for interfaces
From: Ryan McConnehey (mccorywork_at_[hidden])
Date: 2009-05-06 02:12:09

I'm currently trying to fortify my class api by "make interfaces easy to
use correctly and hard to use incorrectly". I have a class as follows.

class api
    api(ConfigName const& configName_, PathName const& pathName_)
    : m_ConfigName(configName_.value)
    , m_PathName(pathName_.value)

    std::string m_ConfigName;
    std::string m_PathName;

Both ConfigName and PathName are typedef to a template structure as follows.

template<typename S>
struct ParameterValue
    ParameterValue(S value_) : value(value_) {}
    S value

typedef ParameterValue<std::string> ConfigName;
typedef ParameterValue<std::string> PathName;

I realized later that this method doesn't prevent the swapping of a
ConfigName with a PathName parameter. Since both parameters are typedef
to the same "type" of ParameterValue they're interchangeable. Is there
a boost class, library or C++ idiom that would provide what I'm looking
for? Since I'm going to be using this concept for other classes I
build, I'd like something that would easily create parameter classes to
use but not be interchangeable with other classes of the same type. I
know that I could do this with a macro but I'm leaving that for a last


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