前向声名

当需要在一个类中用到信赖自身的类定义时，需要用到前向声名，比如下面的例子，注意第1－3行，定义的就是IdlInterface的类，在该类本身就需要引用到InterfaceList但InterfaceList又信赖于IdlInterface，这种定义方法就是前向声名。

 1 class IdlInterface;
 2 typedef std::list<IdlInterface*> InterfaceList;
 3 typedef std::list<IdlInterface*>::iterator InterfaceIterator;
 4 
 5 class IdlInterface : public IdlType {
 6 
 7 private:
 8     /** All functions */
 9     FunctionList __functions;
10     /** Old type's instance */
11     InterfaceList __interfaces;
12 
13 public:
14     /** Adds a new function to interface */
15     void addFunction(IdlFunction*);
16     /** Gets a pointer to current functions list */
17     FunctionList* getFunctions();
18 
19     /** Adds a new interface */
20     void addInterface(IdlInterface*);
21     /** Gets the interface reference */
22     InterfaceList* getInterfaces();
23 
24     /** Casts to std::string for convenience of printing */
25     std::string toString();
26 };