...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
BOOST_FUSION_ADAPT_ASSOC_ADT is a macro than can be used to generate all the necessary boilerplate to adapt an arbitrary class type as a model of Random Access Sequence and Associative Sequence.
BOOST_FUSION_ADAPT_ASSOC_ADT( type_name, (attribute_type0, attribute_const_type0, get_expr0, set_expr0, key_type0) (attribute_type1, attribute_const_type1, get_expr1, set_expr1, key_type1) ... )
The above macro generates the necessary code to adapt type_name
as a model of Random
Access Sequence and Associative
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. 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 class type to be adapted.
#include <boost/fusion/adapted/adt/adapt_assoc_adt.hpp> #include <boost/fusion/include/adapt_assoc_adt.hpp>
namespace demo { struct employee { private: std::string name; int age; public: void set_name(std::string const& n) { name=n; } void set_age(int a) { age=a; } std::string const& get_name()const { return name; } int get_age()const { return age; } }; } namespace keys { struct name; struct age; } BOOST_FUSION_ADAPT_ASSOC_ADT( demo::employee, (std::string const&, std::string const&, obj.get_name(), obj.set_name(val), keys::name) (int, int, obj.get_age(), obj.set_age(val), keys::age)) demo::employee 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;