Re: Template-based database library?
On Sep 18, 10:02 pm, Gerhard Menzl <clcppm-pos...@this.is.invalid>
wrote:
Database-related libraries are conspicuously absent from Boost. Does
anyone know of a template-based, open source, relational database
library that supports the representation of arbitrary relations with
compile-time type safety? Or has such an achievement been found to be
impossible?
I am not looking for a solution that works out of the box (although this
would certainly be nice), but a solid concept that would spare me from
running into too many dead-ends would be welcome.
--
Gerhard Menzl
Non-spammers may respond to my email address, which is composed of my
full name, separated by a dot, followed by at, followed by "fwz",
followed by a dot, followed by "aero".
Take a look at Boost.MultiIndex:
http://www.boost.org/libs/multi_index/doc/examples.html
It has foreign keys support and some other features.
For example:
/* Boost.MultiIndex basic example.
*
* Copyright 2003-2005 Joaqu n M L pez Mu oz.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org/libs/multi_index for library home page.
*/
#if !defined(NDEBUG)
#define BOOST_MULTI_INDEX_ENABLE_INVARIANT_CHECKING
#define BOOST_MULTI_INDEX_ENABLE_SAFE_MODE
#endif
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
using boost::multi_index_container;
using namespace boost::multi_index;
/* an employee record holds its ID, name and age */
struct employee
{
int id;
std::string name;
int age;
employee(int id_,std::string name_,int
age_):id(id_),name(name_),age(age_){}
friend std::ostream& operator<<(std::ostream& os,const employee& e)
{
os<<e.id<<" "<<e.name<<" "<<e.age<<std::endl;
return os;
}
};
/* tags for accessing the corresponding indices of employee_set */
struct id{};
struct name{};
struct age{};
/* see Compiler specifics: Use of member_offset for info on
* BOOST_MULTI_INDEX_MEMBER
*/
/* Define a multi_index_container of employees with following indices:
* - a unique index sorted by employee::int,
* - a non-unique index sorted by employee::name,
* - a non-unique index sorted by employee::age.
*/
typedef multi_index_container<
employee,
indexed_by<
ordered_unique<
tag<id>, BOOST_MULTI_INDEX_MEMBER(employee,int,id)>,
ordered_non_unique<
tag<name>,BOOST_MULTI_INDEX_MEMBER(employee,std::string,name)>,
ordered_non_unique<
tag<age>, BOOST_MULTI_INDEX_MEMBER(employee,int,age)> >
employee_set;
template<typename Tag,typename MultiIndexContainer>
void print_out_by(
const MultiIndexContainer& s,
Tag* =0 /* fixes a MSVC++ 6.0 bug with implicit template function
parms */
)
{
/* obtain a reference to the index tagged by Tag */
const typename
boost::multi_index::index<MultiIndexContainer,Tag>::type& i=
get<Tag>(s);
typedef typename MultiIndexContainer::value_type value_type;
/* dump the elements of the index to cout */
std::copy(i.begin(),i.end(),std::ostream_iterator<value_type>(std::cout));
}
int main()
{
employee_set es;
es.insert(employee(0,"Joe",31));
es.insert(employee(1,"Robert",27));
es.insert(employee(2,"John",40));
/* next insertion will fail, as there is an employee with
* the same ID
*/
es.insert(employee(2,"Aristotle",2387));
es.insert(employee(3,"Albert",20));
es.insert(employee(4,"John",57));
/* list the employees sorted by ID, name and age */
std::cout<<"by ID"<<std::endl;
print_out_by<id>(es);
std::cout<<std::endl;
std::cout<<"by name"<<std::endl;
print_out_by<name>(es);
std::cout<<std::endl;
std::cout<<"by age"<<std::endl;
print_out_by<age>(es);
std::cout<<std::endl;
return 0;
}
--
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