Terms 25: Sending Constructor and Non-Member Functions
Virtual constructor: This noun is a little horrible. The C constructor does not allow virtual, then what kind of meaning is this virtual constructor?
Consider the following code:
Class base // base class
{
}
Class Derivea: Public Base
{
}
Class Deriveb: Public Base
{
}
Class Classset
{
PUBLIC:
Classset (ISTREAM & STR)
{
While (STR)
Components.push_back (getObject (STR))
}
Static Base * GetObject (istream & Str);
Private:
Vector
}
The so-called virtual constructor is the constructor of class Classset, which enables Components to be initialized to various types of inheritance class. This is the so-called virtual constructor, I look very similar to the object factory. In the past program design, this is what we often use.
Consider the following code:
Class base // base class
{
Virtual base * clone () const = 0;
}
Class Derivea: PUBLIC BASE
{
Virtual Derivea * Clone () Const
{Return New Derivea (* this);
}
Class Deriveb: Public Base
{
Virtual Deriveb * Clone () Const
{RETURN New Deriveb (* this);
}
Class Classset
{
PUBLIC:
Classset (Const Classset & RHS)
{
/ / There is a bug here, rhs.components.begin () is illegal
For (Vector
Components.push_back ((* iter) -> clone);
}
Static Base * GetObject (istream & Str);
Private:
Vector
}
Is this called a virtual copy constructor? I have no problem in this code now, I need to pay attention to deepening the STL.
The virtualization of non-member functions is very simple, just writes a virtual function to do actual work, then write a non-member function, it is only responsible for calling the virtual function. In order to reduce costs, non-member functions can be inline.
Consider the following code
Class base // base class
{
Virtual Ostream * Print (Ostream & S) Const = 0;
}
Class Derivea: Public Base
{
Virtual Ostream * Print (Ostream & S) Const
{Return New Derivea (* this);
}
Class Deriveb: Public Base
{
Virtual Ostream * Print (Ostream & S) Const}
}
Inline Operator << (Ostream & S, Const Base & C)
{
Return C.Print (s);
}
