C ++ design mode-iterator Mode

Iterator: provides a method to access each element of an aggregate object sequentially without exposing the internal representation of the object.

 

Iterator mode structure:

 

 

 

Typedef String object;

Abstract class of Iterator:

 

Class Iterator

{

Public:

Virtual object & First () = 0;

Virtual object & Next () = 0;

Virtual bool IsDone () = 0;

Virtual object & CurrentItem () = 0;

};

// Defines the start object, obtains the next object, determines whether to end, current object, and other abstract methods, unified interface

 

Aggregate abstract class of Aggregate:

 

Class Aggregate

{

Public:

Virtual Iterator * CreateIterator () = 0; // create an Iterator

};

 

 

ConcreteIterator: a specific Iterator class that inherits Iterator

 

Class ConcreteIterator: public Iterator

{

Private:

ConcreteAggregate * aggregate;

List <object >:: iteratorit;

Public:

ConcreteIterator (ConcreteAggregate * aggregate)

{

This-> aggregate = aggregate;

It = aggregate-> begin ();

}

 

Object & First ()

{

Return * it;

}

 

Object & Next ()

{

Object ret = NULL;

If (++ it )! = Aggregate-> end ())

Ret = * it;

Return ret;

}

 

Bool IsDone ()

{

If (++ it )! = Aggregate-> end ())

Return false;

Else

Return true;

}

 

Object & CurrentItem ()

{

Return * it;

}

};

 

 

ConcreteAggregate: a specific aggregation class that inherits Aggregate.

 

Class ConcreteAggregate: public Aggregate

{

Private:

List <object> * items = new list <object> ();

Public:

Iterator * CreateIterator ()

{

Return new ConcreteIterator (ConcreteAggregate * paggregate = this );

}

Void setObject (object obj)

{

Items-> push_back (obj );

}

};

 

Client code:

 

Void main ()

{

ConcreteAggregate * pa = newConcreteAggregate ();

Pa-> setObject ("element 1 ");

Pa-> setObject ("element 2 ");

Pa-> setObject ("element 3 ");

Pa-> setObject ("element 4 ");

Iterator * it = pa-> CreateIteraor (pa );

Cout <it-> First ();

While (! It-> IsDone ())

{

Cout <it-> CurrentItem () <endl;

It-> Next ();

}

 

}