IcalObject methods are const

ical/IcalObject.cpp

@@ -5,11 +5,11 @@ namespace ical {
     events.push_back(event);
   }
 
-  std::vector<ical::Event*> IcalObject::get_events() {
+  std::vector<ical::Event*> IcalObject::get_events() const {
     return events;
   }
 
-  bool IcalObject::empty() {
+  bool IcalObject::empty() const {
     return events.size() == 0;
   }
 

ical/IcalObject.h

@@ -12,8 +12,8 @@ namespace ical {
   class IcalObject {
     public:
       void add_event(ical::Event* event);
-      std::vector<ical::Event*> get_events();
-      bool empty();
+      std::vector<ical::Event*> get_events() const;
+      bool empty() const;
 
       friend std::ostream& operator<<(std::ostream &os, ical::IcalObject const &obj);
     private: