From: Joseph Fradley (joe.fradley_at_[hidden])
Date: 2008-01-29 13:42:22
Joseph Fradley wrote:
>
> I have a problem that I would like to solve in the most generic
> non-intrusive way possible (such as boost serialization). What I want
> is to access class members both via it's initially designed accessors
> but also via a "const char *" key. In addition, I want to pass list
> of key's (via a vector of const char * or a single delimited multikey
> char *) to get nested member access.
>
> For example:
> ...
> // these should be equivalent
> Point p;
> int val;
> val = p.x;
> val = p.getX();
> p.getMemberValue("x", val);
>
> // there also
> Rectangle r;
> int val;
> Point pVal;
> r.getMemberValue("corner:x", val);
> r.getMemberValue("corner", pVal);
>
Steven Watanabe wrote:
>You could try something along these lines:
>
>class indexable_base {
>public:
> virtual indexable_base* lookup(const char*) = 0;
> virtual const std::type_info& get_type() = 0;
> virtual void* get() = 0;
>};
>
>Then you can put macros in the derived class like so:
>
>class Rectangle : public indexable_base {
> DEFINE_LOOKUP() {
> DECLARE_VARIABLE(corner);
> }
> Point Corner;
>};
>
>Which would expand to something like
>
>class Rectangle : public indexable_base {
> template<class T>
> void getMemberValue(const char* key, T& out) {
> indexable_base result = lookup(key);
> if(typeid(T) == result->get_type()) {
> out = *(static_cast<T*>(result->get()))
> } else {
> throw(std::bad_cast());
> }
> }
> indexable_base* lookup(const char* key) {
> // split key at ":" and lookup call lookup_ recursively until
>all the keys are used up.
> }
> static void init() {
> map_.insert(std::make_pair("corner",
>&boost::bind(&Rectangle::corner, _1)));
> }
> Point corner;
>};
>
Steven,
Thank you, I'm trying it now. But I'm a confused as to what type of
map to create from your line :
map_.insert(std::make_pair("corner", &boost::bind(&Rectangle::corner, _1)));
I've just now read up on boost::bind and I can only see documentation
of binding to member functions not member data. Could you elaborate?
Joe