/**
A collection of objects that can be loaded from a datafile. Each object is
identified by a name, which must be unique across the entire collection.
+
+While this class can be instantiated by itself and used for storing objects,
+loading requires that a subclass defines the supported types. See the add_type
+method for details.
+
+Collections also support a notion of "future objects". These are objects which
+are known to be possible to load, but loading them is deferred to the first
+time they are requested.
*/
class Collection
{
public:
/**
- Loads objects into a Collection.
+ Loads objects into a Collection. Automatically picks up keywords from
+ defined item types.
*/
class Loader: public DataFile::Loader
{
Collection() { }
virtual ~Collection();
- /**
- Adds an object into the collection. If a name collision occurs, an
- exception is thrown. The collection takes ownership of the object.
- */
+ /** Adds an object into the collection. The name must not pre-exist. The
+ collection takes ownership of the object. */
template<typename T>
void add(const std::string &name, T *item)
{
if(!item)
throw std::invalid_argument("Collection::add(item)");
- RefPtr<typename RemoveConst<T>::Type> ptr(item);
- try
- {
- insert_unique(items, name, ptr);
- }
- catch(...)
+ typedef RefPtr<typename RemoveConst<T>::Type> RPNCT;
+
+ ItemMap::iterator i = items.find(name);
+ if(i!=items.end())
{
- // Avoid deleting the object
- ptr.release();
- throw;
+ if(i->second.check_type<RPNCT>())
+ {
+ // Replace a future object placeholder
+ RPNCT &ptr = i->second.value<RPNCT>();
+ if(!ptr)
+ {
+ ptr = item;
+ return;
+ }
+ }
+
+ throw key_error(typeid(ItemMap));
}
+
+ items.insert(ItemMap::value_type(name, RPNCT(item)));
}
- /**
- Gets an object of a specific type from the collection.
- */
+protected:
+ /** Adds the name of a future object to the collection. The object itself
+ will be loaded on first access. The calling subclass should be prepared to
+ create the object on request. */
+ template<typename T>
+ void add_future(const std::string &name)
+ {
+ RefPtr<typename RemoveConst<T>::Type> ptr(0);
+ insert_unique(items, name, ptr);
+ }
+
+public:
+ /// Gets a typed object from the collection.
template<typename T>
T &get(const std::string &name) const
{
typedef typename RemoveConst<T>::Type NCT;
- return *get_item(items, name).value<RefPtr<NCT> >();
+ T *ptr = get_item(items, name).value<RefPtr<NCT> >();
+ if(!ptr)
+ throw key_error(typeid(ItemMap));
+ return *ptr;
}
- /**
- Gets an object of a specific type from the collection. If the name is not
- found in the collection and there is a creator for the item type, it is
- invoked.
- */
+ /** Gets a typed object from the collection. If the name is not found in
+ and a creator for the item type is defined, it is invoked. */
template<typename T>
T &get(const std::string &);
- /**
- Returns a list of the names of objects of a specific type in the collection.
- */
+private:
+ template<typename T>
+ void collect_items(std::list<T *> *objects, std::list<std::string> *names, std::list<std::string> *future_names)
+ {
+ typedef RefPtr<typename RemoveConst<T>::Type> RPNCT;
+
+ for(ItemMap::const_iterator i=items.begin(); i!=items.end(); ++i)
+ if(i->second.check_type<RPNCT>())
+ {
+ T *ptr = i->second.value<RPNCT>().get();
+ if(ptr)
+ {
+ if(objects)
+ objects->push_back(ptr);
+ if(names)
+ names->push_back(i->first);
+ }
+ else if(future_names)
+ future_names->push_back(i->first);
+ }
+ }
+
+public:
+ /** Returns a list of the names of loaded objects of one type in the
+ collection. */
template<typename T>
std::list<std::string> get_names() const
{
std::list<std::string> result;
- for(ItemMap::const_iterator i=items.begin(); i!=items.end(); ++i)
- if(i->second.check_type<RefPtr<typename RemoveConst<T>::Type> >())
- result.push_back(i->first);
+ collect_items<T>(0, &result, 0);
return result;
}
- /**
- Returns a list of objects of a specific type in the collection.
- */
+ /** Returns a list of the names of objects of one type in the collection,
+ including any future objects. */
+ template<typename T>
+ std::list<std::string> get_names()
+ {
+ std::list<std::string> result;
+ collect_items<T>(0, &result, &result);
+ return result;
+ }
+
+ /// Returns a list of loaded objects of one type in the collection.
template<typename T>
std::list<T *> get_list() const
{
- typedef RefPtr<typename RemoveConst<T>::Type> RPNCT;
+ std::list<T *> result;
+ collect_items<T>(&result, 0, 0);
+ return result;
+ }
+ /** Returns a list of objects of one type in the collection. Any future
+ objects of that type are loaded and returned in the list. */
+ template<typename T>
+ std::list<T *> get_list()
+ {
std::list<T *> result;
- for(ItemMap::const_iterator i=items.begin(); i!=items.end(); ++i)
- if(i->second.check_type<RPNCT>())
- result.push_back(i->second.value<RPNCT>().get());
+ std::list<std::string> future;
+ collect_items<T>(&result, 0, &future);
+ for(std::list<std::string>::iterator i=future.begin(); i!=future.end(); ++i)
+ result.push_back(&get<T>(*i));
return result;
}
- /**
- Checks whether a name exists in the collection. Does not care about the
- type of the object.
- */
- bool contains(const std::string &n) const;
+private:
+ template<typename T>
+ unsigned get_status(const std::string &name) const
+ {
+ ItemMap::const_iterator i = items.find(name);
+ if(i==items.end())
+ return false;
- /**
- Returns the name of an item in the collection.
- */
+ typedef RefPtr<typename RemoveConst<T>::Type> RPNCT;
+ if(!i->second.check_type<RPNCT>())
+ return false;
+
+ T *ptr = i->second.value<RPNCT>().get();
+ return ptr ? 1 : 2;
+ }
+
+public:
+ /// Checks whether a typed object exists and is loaded in the collection.
+ template<typename T>
+ bool contains(const std::string &name) const
+ { return get_status<T>(name)==1; }
+
+ /** Checks whether a typed object exists in the collection, as either a
+ loaded or future object. */
+ template<typename T>
+ bool contains(const std::string &name)
+ { return get_status<T>(name)>0; }
+
+ /// Returns the name of an item in the collection.
template<typename T>
const std::string &get_name(T *d) const
{
}
protected:
+ /** Adds a type to the collection. The returned descriptor object reference
+ can be used to define how objects of that type can be loaded. */
template<typename T>
CollectionItemType<T> &add_type();
};
template<typename T>
class Tag: public TagBase
- {
- public:
- virtual ~Tag() { }
- };
+ { };
std::string kwd;
TagBase *tag;
- CollectionItemTypeBase(): tag(0) { }
+ CollectionItemTypeBase();
public:
- virtual ~CollectionItemTypeBase()
- { delete tag; }
+ virtual ~CollectionItemTypeBase();
virtual void add_to_loader(Collection::Loader &) const = 0;
virtual bool can_create() const = 0;
};
+/**
+Describes a type of item that can be loaded by a Collection. These are created
+by Collection::add_type.
+*/
template<typename T>
class CollectionItemType: public CollectionItemTypeBase
{
delete store;
}
+ /** Sets a datafile keyword for this item type. The Collection's loader
+ will accept a statement with this keyword and a single string argument - the
+ item's name. */
CollectionItemType &keyword(const std::string &k)
{
kwd = k;
return *this;
}
+ /** Attaches a creator function to this item type. If an item is not found
+ in the Collection, the creator function for its type is called to create it.
+ The function must be a member of the Collection subclass containing the
+ type. It must return the created object, or null if it could not be
+ created. It's also permissible to load the item via other means and then
+ return null. */
template<typename C>
CollectionItemType &creator(T *(C::*func)(const std::string &))
{
return *this;
}
+ /** Specifies the storage type for items of this type. It must be a base
+ class of the actual type. */
template<typename S>
CollectionItemType &store_as()
{
{
typedef typename RemoveConst<T>::Type NCT;
- if(!items.count(name))
+ ItemMap::iterator i = items.find(name);
+ if(i!=items.end())
{
- for(TypeList::iterator i=types.begin(); i!=types.end(); ++i)
- if((*i)->can_create() && (*i)->check_type<NCT>())
- (*i)->create_item(*this, name);
+ NCT *ptr = i->second.value<RefPtr<NCT> >().get();
+ if(ptr)
+ return *ptr;
}
+ for(TypeList::iterator j=types.begin(); j!=types.end(); ++j)
+ if((*j)->can_create() && (*j)->check_type<NCT>())
+ (*j)->create_item(*this, name);
+
return *get_item(items, name).value<RefPtr<NCT> >();
}
projects / libs / datafile.git / blobdiff