[niepce] Add string conversion helpers for property values

[Hubert Figuière <hub src gnome org>]

commit 4996afe07145f94fe1bb2263cea36b75ce79ef94
Author: Hubert Figuière <hub figuiere net>
Date:   Thu Jun 27 00:26:23 2013 -0400

    Add string conversion helpers for property values

 src/fwk/base/propertybag.cpp |   10 ++++++++++
 src/fwk/base/propertybag.hpp |    3 +++
 2 files changed, 13 insertions(+), 0 deletions(-)
---
diff --git a/src/fwk/base/propertybag.cpp b/src/fwk/base/propertybag.cpp
index 29bb8c5..61eccf4 100644
--- a/src/fwk/base/propertybag.cpp
+++ b/src/fwk/base/propertybag.cpp
@@ -33,11 +33,21 @@ bool is_integer(const PropertyValue & v)
     return v.type() == typeid(int);
 }
 
+bool is_string(const PropertyValue & v)
+{
+    return v.type() == typeid(std::string);
+}
+
 int get_integer(const PropertyValue & v)
 {
     return is_empty(v) ? 0 : boost::get<int>(v);
 }
 
+const std::string & get_string(const PropertyValue & v)
+{
+    return boost::get<std::string>(v);
+}
+
 bool PropertyBag::set_value_for_property(PropertyIndex idx, const PropertyValue & value)
 {
     bool removed = (m_bag.erase(idx) == 1);
diff --git a/src/fwk/base/propertybag.hpp b/src/fwk/base/propertybag.hpp
index 9018d96..5f62031 100644
--- a/src/fwk/base/propertybag.hpp
+++ b/src/fwk/base/propertybag.hpp
@@ -45,8 +45,11 @@ typedef std::set<PropertyIndex> PropertySet;
 bool is_empty(const PropertyValue & v);
 /** Return if it is an integer */
 bool is_integer(const PropertyValue & v);
+bool is_string(const PropertyValue & v);
 /** Return the integer value (or 0 if empty) */
 int get_integer(const PropertyValue & v);
+/** Return the string value */
+const std::string & get_string(const PropertyValue & v);
 
 /** a property bag
  * It is important that the values for PropertyIndex be properly name spaced