BOOST_FUSION_ADAPT_ASSOC_TPL_ADT is a macro than can be used to generate all the necessary boilerplate to adapt an arbitrary template class type as a model of Random Access Sequence and Associative Sequence.

Synopsis

BOOST_FUSION_ADAPT_ASSOC_TPL_ADT(
    (template_param0)(template_param1)...,
    (type_name) (specialization_param0)(specialization_param1)...,
    ([attribute_type0, attribute_const_type0,] get_expr0, set_expr0, key_type0)
    ([attribute_type1, attribute_const_type1,] get_expr1, set_expr1, key_type1)
    ...
    )

Expression Semantics

The above macro generates the necessary code to adapt type_name or an arbitrary specialization of type_name as a model of Random Access Sequence and Associative Sequence. The sequence (template_param0)(template_param1)... declares the names of the template type parameters used. The sequence (specialization_param0)(specialization_param1)... declares the template parameters of the actual specialization of type_name that is adapted as a fusion sequence. The sequence of ([attribute_typeN, attribute_const_typeN, get_exprN, set_exprN, key_typeN)] 5-tuples declares the types, const types, get-expressions, set-expressions and key types of the elements that are part of the adapted fusion sequence. get_exprN is the expression that is invoked to get the Nth element of an instance of type_name. This expression may access a variable named obj of type type_name& or type_name const& which represents the underlying instance of type_name. attribute_typeN and attribute_const_typeN may specify the types that get_exprN denotes to, when omitted the type is deduced from [get_exprN] return type via BOOST_TYPEOF. On compiler missing support for variadic macros auto can be used to avoid repeating the type. set_exprN is the expression that is invoked to set the Nth element of an instance of type_name. This expression may access variables named obj of type type_name&, which represent the corresponding instance of type_name, and val of an arbitrary const-qualified reference template type parameter Val, which represents the right operand of the assignment expression.

The actual return type of fusion's intrinsic sequence access (meta-)functions when in invoked with (an instance of) type_name is a proxy type. This type is implicitly convertible to the attribute type via get_exprN and forwards assignment to the underlying element via set_exprN. The value type (that is the type returned by result_of::value_of, result_of::value_of_data, result_of::value_at, result_of::value_at_c and result_of::value_at_key) of the Nth element is attribute_typeN with const-qualifier and reference removed.

The macro should be used at global scope, and type_name should be the fully namespace qualified name of the template class type to be adapted.

Header

#include <boost/fusion/adapted/adt/adapt_assoc_adt.hpp>
#include <boost/fusion/include/adapt_assoc_adt.hpp>

Example

namespace demo
{
    template<typename Name, typename Age>
    struct employee
    {
    private:
        Name name;
        Age age;

    public:
        void set_name(Name const& n)
        {
            name=n;
        }

        void set_age(Age const& a)
        {
            age=a;
        }

        Name const& get_name()const
        {
            return name;
        }

        Age const& get_age()const
        {
            return age;
        }
    };
}

namespace keys
{
    struct name;
    struct age;
}

BOOST_FUSION_ADAPT_ASSOC_TPL_ADT(
    (Name)(Age),
    (demo::employee) (Name)(Age),
    (Name const&, Name const&, obj.get_name(), obj.set_name(val), keys::name)
    (Age const&, Age const&, obj.get_age(), obj.set_age(val), keys::age))

demo::employee<std::string, int> e;
at_key<keys::name>(e)="Edward Norton";
at_key<keys::age>(e)=41;
//Prints 'Edward Norton is 41 years old'
std::cout << e.get_name() << " is " << e.get_age() << " years old" << std::endl;

See also

adt_attribute_proxy