From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 7 Dec 2012 10:28:15 +0000 (+0200)
Subject: Add support for fallback collections
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=a5d5fa04bcbe360fc55fdb25b45937b29fb5c9cd;p=libs%2Fdatafile.git

Add support for fallback collections
---

diff --git a/source/collection.cpp b/source/collection.cpp
index fbe894a..0709919 100644
--- a/source/collection.cpp
+++ b/source/collection.cpp
@@ -5,6 +5,10 @@ using namespace std;
 namespace Msp {
 namespace DataFile {
 
+Collection::Collection():
+	fallback(0)
+{ }
+
 Collection::~Collection()
 {
 	for(TypeList::iterator i = types.begin(); i!=types.end(); ++i)
@@ -30,6 +34,16 @@ const Variant &Collection::get_var(const string &name, const CollectionItemTypeB
 			(*j)->load(*this, *type, name);
 			loaded = items.count(name);
 		}
+		if(!loaded && fallback)
+		{
+			for(TypeList::const_iterator j=fallback->types.begin(); j!=fallback->types.end(); ++j)
+				if((*j)->is_same_type(*type))
+				{
+					if(fallback->get_status(name, **j))
+						return fallback->get_var(name, *j);
+					break;
+				}
+		}
 	}
 
 	return get_item(items, name);
@@ -99,6 +113,11 @@ void Collection::load_items_from_sources(const CollectionItemTypeBase &type)
 	}
 }
 
+void Collection::set_fallback(Collection *f)
+{
+	fallback = f;
+}
+
 
 Collection::Loader::Loader(Collection &c):
 	coll(c)
diff --git a/source/collection.h b/source/collection.h
index bbde9f9..ee7eb46 100644
--- a/source/collection.h
+++ b/source/collection.h
@@ -45,6 +45,11 @@ method for details.
 
 Collections can have sources for loading objects on demand.  Automatic loading
 only works on a non-const Collection.  See class CollectionSource for details.
+
+A fallback collection can be designated as another way of loading items that
+are not present.  Items retrieted from the fallback collection are shared
+between the collections, and are only deleted when all collections in the chain
+have been destroyed.
 */
 class Collection
 {
@@ -86,11 +91,12 @@ private:
 	TypeList types;
 	ItemMap items;
 	SourceList sources;
+	Collection *fallback;
 
 	Collection(const Collection &);
 	Collection &operator=(const Collection &);
 public:
-	Collection() { }
+	Collection();
 	virtual ~Collection();
 
 	/** Adds an object into the collection.  The name must not pre-exist.  The
@@ -262,6 +268,11 @@ private:
 	void gather_names_from_sources(std::list<std::string> &, const CollectionItemTypeBase &) const;
 
 	void load_items_from_sources(const CollectionItemTypeBase &);
+
+protected:
+	/** Sets a fallback collection, which will be consulted if an item is not
+	found. */
+	void set_fallback(Collection *);
 };
 
 template<typename T>
@@ -309,6 +320,7 @@ public:
 	const std::string &get_keyword() const { return kwd; }
 	void add_suffix(const std::string &);
 	bool match_name(const std::string &) const;
+	virtual bool is_same_type(const CollectionItemTypeBase &) const = 0;
 	virtual bool check_item_type(const Variant &) const = 0;
 	virtual void add_to_loader(Collection::Loader &) const = 0;
 	virtual bool can_create() const = 0;
@@ -423,6 +435,9 @@ public:
 		return *this;
 	}
 
+	virtual bool is_same_type(const CollectionItemTypeBase &other) const
+	{ return dynamic_cast<const CollectionItemType<T> *>(&other); }
+
 	virtual bool check_item_type(const Variant &var) const
 	{ return var.check_type<RefPtr<T> >(); }