Design Pattern Example 4 observer (observer) and iterator (iterator)

The reason for putting these two modes together is the relationship between C # statements. These two modes become easy or different.

Observer (observer)

Class Observer
{
Public Delegate Void Eventhandler (string State );
Public Event eventhandler changeevent;

Public   Void Changestate (string state)
{
If (Changeevent ! =   Null )
{
Changeevent (State );
}
}
}

Call Static   Void Main ( String [] ARGs)
{
Observer obs =   New Observer ();
Obs. changeevent + =   New Observer. eventhandler (obs_changeevent );
Obs. changestate ( " Change " );
Console. Read ();
}

Static   Void Obs_changeevent ( String State)
{
Console. writeline ("I see:" +State );
}

Running result

Iterator (iterator)
Classes that implement the ienumerable and ienumerator interfaces respectivelyPublic   Class Tokens: ienumerable
{
Public   String [] Elements;

Public Tokens ( String Source, Char [] Delimiters)
{
Elements=Source. Split (delimiters );
}

Public Ienumerator getenumerator ()
{
Return NewTokenenumerator (This);
}

}

Public   Class Tokenenumerator: ienumerator
{
Private   Int Position =   - 1 ;
Private Tokens T;

Public Tokenenumerator (tokens T)
{
This. T=T;
}

Public   Bool Movenext ()
{
If (Position < T. elements. Length -   1 )
{
Position++;
Return True;
}
Else
{
Return False;
}
}

Public   Void Reset ()
{
Position= -1;
}

Public   Object Current
{
Get
{
ReturnT. elements [position];
}
}
}

Call Static   Void Main ( String [] ARGs)
{
Tokens =   New Tokens ( " A, B, c " , New   Char [] {','} );
Ienumerator iterator = Tokens. getenumerator ();
While (Iterator. movenext ())
{
String Token = Iterator. Current As   String ;
If (Token ! =   Null )
{
Console. writeline (token );
}
}
Console. Read ();
}

C # generic support makes iterator implementation better.
Result