C + + iterator/Walker iterator implementation

1. Principle

An iterator, also called a walker, is used to access the data in the container, which is designed to bridge the access between the algorithm and the container, thus separating the algorithm from the data, without worrying about the specific storage details of the data. Please refer to the following two blogs for a detailed description of the principle:

[1]. C + + iterator iterator

[2]. iterator Mode C + + implementation

UML diagram for iterators:

(From: http://www.cnblogs.com/yc_sunniwell/archive/2010/06/25/1764934.html)

2. Implement

Based on the above schematic diagram, a simple iterator is implemented below.

/** The following implements a container iterator (accessor)*/#include<boost/assert.hpp>#include<iostream>using namespacestd;//iterator base classTemplate<typename t>classIterater { Public:  Virtual~Iterater () {}Virtual voidFirst () =0; Virtual voidNext () =0; Virtual BOOLIsDone () =0; VirtualT CurrentItem () =0;};//container base classTemplate<typename t>classAggregate { Public:  Virtual~Aggregate () {}Virtualiterater<t>* createiterater () =0; Virtual intGetSize () =0; VirtualT GetItem (intNIndex) =0;};//Specific iteratorsTemplate<typename t>classConcreateiterater: PublicIterater<t> { Private: Aggregate<t>*P_; intcur_index_; Public: Concreateiterater (Aggregate<t>*agregate): Cur_index_ (0), P_ (agregate) {}~Concreateiterater () {}voidFirst () {cur_index_=0; }  voidNext () {if(Cur_index_ < p_->GetSize ()) {Cur_index_++; }  }  BOOLIsDone () {if(Cur_index_ > P_->getsize ()-1) {      return true; }    return false; } T CurrentItem () {returnP_->GetItem (cur_index_); }};//Specific iteratorsTemplate<typename t>classConcreateaggregate: PublicAggregate<t> {  Public: Concreateaggregate (intnSize): Size_ (NSize), Data_ (NULL) {Data_=NewT[nsize];  for(inti =0; i < nSize; i++) {Data_[i]=i; }} iterater<t>*Createiterater () {return NewConcreateiterater<t> ( This); }  intGetSize () {returnSize_; } T GetItem (intNIndex) {    if(NIndex <0|| NIndex >=size_)return(T) (-1); returnData_[nindex]; }  Public:  intSize_; T*Data_;};intMainintargcChar**argv) {Aggregate<Double>* Pag =Newconcreateaggregate<Double> (Ten); Iterater<Double>* Pcon = Pag->createiterater ();//1 of 2//cxk::iterater<int>* Pcon = new cxk::concreateiterater<int> (PAG);//2 of 2cout <<"All value:"<<Endl;  for(Pcon->first ();!pcon->isdone (); pcon->Next ()) {cout<<"Value:"<< Pcon->currentitem () <<Endl; }  return 0;}

3. Results

All Value:value: 0 Value: 1 Value: 2 Value: 3 Value: 4 Value: 5 Value: 6 Value: 7 Value: 8 Value: 9

All Value:value:0value:1value:2value:3value:4value:5value:6value:7value:8value:9

C + + iterator/Walker iterator implementation