There are two ways to get MongoDB support into your crails project:
If you haven't created the application yet, then use the --use-mongodb option provided by the crails create command.
If the application already exists, then you need to make the following changes to the CMakeLists.txt file:
# Add this line at the beginning of the file
set(crails_mongodb_dep mongoclient crails-mongodb)
# Add ${crails_mongodb_dep} to the call to `target_link_library`
target_link_libraries(crails-app
crails-core ${Boost_LIBRARIES} pthread dl crypto Boots ${CPPNETLIB_LIBRARIES}
${crails_mongodb_dep})#ifndef USER_HPP
# define USER_HPP
# include <crails/mongodb/model.hpp>
# include <crails/password.hpp>
class User : public MongoDB::Model
{
// MONGODB_COLLECTION defines the names of the database (as specified in `conf/db.json`) and collection to use.
MONGODB_COLLECTION(mongodb, users);
// MONGODB_MODEL generates constructors, destructor, and the Find and Create methods.
MONGODB_MODEL(User);
// MONGODB_FIELD generates a getter and a setter (respectively `type name() const` and `void set_name(type)`)
MONGODB_FIELD(std::string, name, "")
MONGODB_FIELD(Password, password, "")
};We will now see how to use the model we just created by writing the code for a UserController.
void UserController::show()
{
std::string id = params["id"].Value();
SP(User) user = User::Find(id);
if (user.Null())
{
response["status"] = 404;
return ;
}
*shared_vars["user"] = user.Pointer();
render("layouts/application", "users/show");
}void UserController::create()
{
if (params["user"]["name"].Value() != "" &&
params["user"]["password"].Value() != "" &&
password_matches_confirmation())
{
auto user = User::Create(params["user"]);
user.Save();
*shared_vars["user"] = &user;
render("layouts/application", "users/show");
}
}void UserController::update()
{
SP(User) user = User::Find(params["id"]);
bool success = true;
if (params["user"]["name"].Value() != "")
user->set_name(params["user"]["name"]);
if (params["user"]["password"].Value() != "")
{
if (password_matches_confirmation())
user->set_password(params["user"]["password"]);
else
success = false;
}
if (success)
{
user->save();
*shared_vars["user"] = user.Pointer();
render("layouts/application", "users/show");
}
else
response["status"] = 422;
}
bool UserController::password_matches_confirmation()
{
return (params["password"].Value() && params["password-confirm"].Value());
}void UserController::delete()
{
SP(User) user = User::Find(params["id"]);
user->Remove();
}Relations connect your models together, greatly simplifying the task of querying objects that are related to each other.
A one-to-many relationship is represented using the MONGODB_HAS_MANY macro:
class User : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, users);
MONGODB_MODEL(User);
MONGODB_FIELD(std::string, name, "")
MONGODB_FIELD(Password, password, "")
MONGODB_HAS_MANY(Comment, user)
};MONGODB_HAS_MANY takes two parameters: the type of the related model, and the name of the "inverse". In this example,
we create a case were MONGODB_HAS_MANY will look for a user_id field in the Comment model that matches the id of
the current object.
Belongs to is the reverse of a "has_many" relationship. It helps you manage the field.
class Comment : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, comments);
MONGODB_MODEL(Comment);
MONGODB_FIELD(std::string, message, "")
MONGODB_BELONGS_TO(User)
};This helper will create the methods void set_user(const User&) and SP(User) get_user() const.
You may also customize the name of the relationship, like this:
class User : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, users)
MONGODB_MODEL(User)
MONGODB_FIELD(std::string, name, "")
MONGODB_FIELD(Password, password, "")
MONGODB_HAS_MANY(Comment, author)
};
class Comment : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, comments)
MONGODB_MODEL(Comment)
MONGODB_FIELD(std::string, message, "")
MONGODB_BELONGS_TO_AS(User, author)
};Now, the generated methods will be void set_author(const User&) and SP(User) get_author() const, and the field in the comments collection will have an author_id field instead of the user_id field.
Has and belongs to many relationships are similar, but one of the model has to host the relationship.
class Player : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, players)
MONGODB_MODEL(Player)
MONGODB_HAS_AND_BELONGS_TO_MANY(Game,game,player) // typename, relation name, foreign relation name
}
class Game : public MongoDB::Model
{
MONGODB_COLLECTION(mongodb, games)
MONGODB_MODEL(Game)
MONGODB_HAS_AND_BELONGS_TO_MANY_HOST(Player,player) // typename, relation name
}The generated methods will be:
SmartPointer<Criteria<Game> > Player::get_games();
void Player::add_to_games(Game&) const;
void Player::remove_from_games(Game&) const;
SmartPointer<Criteria<Player> > Game::get_players();
void Game::add_to_players(const Player&);
void Game::remove_from_players(const Player&);
MongoDB::Array<mongo::OID> Game::get_players_ids() const;
void Game::set_players_ids(MongoDB::Array<mongo::OID>);
Don't forget that no matter on which object you call the add_to_... and remove_from_... methods, the modifications are always made on the host (Game in this case). When you want to save your modifications, do not forget to call Save on the host object.
When your requirements are a bit more specific, you'll need to make your own requests. You may use helpers from the Criteria template to achieve this:
#include <Boots/Utils/smart_pointer.hpp> // defines the SP macro
void MyController::get_by_name()
{
std::string name = params["name"];
SP(Criteria<User>) results = Criteria<User>::prepare(MONGO_QUERY("name" << name));
std::stringstream text;
text << "Found " << results->count() << " users with name `" << name '`' << std::endl;
render(TEXT, text);
}A simple documentation for the mongo::Query object is available here.
You may also iterate on the results using Criteria<T>::Each(std::function<bool(T&)>).
void MyController::get_by_name()
{
std::string name = params["name"];
SP(Criteria<User>) results = Criteria<User>::prepare(MONGO_QUERY("name" << name));
std::stringstream text;
results->each([&text](User& user) -> bool {
text << "User(" << user.Id() << ") matching name" << std::endl;
return (true); // you may return 'false' if you wish to interrupt the loop
});
render(TEXT, text);
}You may also only fetch a subset of the results, using pagination:
std::list<User> MyController::get_user_page(int page, int items_per_pages)
{
SP(Criteria<User>) results = Criteria<User>::prepare();
results->set_skip(page * items_per_pages);
results->set_limit(items_per_pages);
return results->entries();
}