Wrapper Class

                                   What is the wrapper class

1. What is the Wrapper class:  A Wrapper class is a container class, a data structure, or an abstract data type whose instances are collections of other objects. You can wrap different objects types or any other types in a wrapper class.

  in simpler words, wrapper could be thought of as temporary holder/buffer for information lying across different tables queried via a SOQL.

1. Why we used wrapper class: Generally collections like "list" can store only one type of data for example "string' or "Account". List<Account> will hold only accounts and List<string> will hold only strings in it. But what if you want to show data on the table that should show account record as well as it primary contact data  ? iterating over List<Account> will only allow account records and no contact data. 

In this case, you can create a wrapper class having variables account and contact and then create the list of that wrapper class. This may look a bit complicated but as you go through an example it will sort out easily.

   Example of wrapper class:

Apex class:

public class Wrapharsh {

//CONTROLLER CLASS

   //Our collection of the class/wrapper objects wrapaccount

    public list<wrapaccount> wrapaccountList { get; set; }

    //We create a new list of Accounts that we be populated only with Accounts if they are selected

    public list<account> selectedAccounts{get;set;}    

      

      public Wrapharsh ()
    {

          wrapaccountList =new list<wrapaccount>();

         // As each account is processed we create a new wrapaccount object and add it to the accountlist

          for(account a:[select id,name,billingcity,phone from account limit 10]){

           wrapaccountlist.add(new wrapaccount(a));

        

           }

      }

    //### SELECTED ACCOUNT SHOWN BY THIS METHOD

      public void ProcessSelected(){

     selectedAccounts=new list<account>();

     

      for(wrapaccount wrapobj:wrapaccountlist){

           if(wrapobj.isSelected==true){

           selectedAccounts.add(wrapobj.accn);

           }

            

         }

      }

      

  //##THIS IS WRAPPER CLASS

   // account and checkbox taken in wrapper class

   

   public class wrapaccount{

    

    public account accn{get;set;}

    public boolean isSelected{get;set;}

   
     //This is the contructor method. When we create a new wrapaccount object we pass a Account that is set to the accn property. We also set the selected value to false

       public wrapaccount(account a){

     

         accn=a;

         isselected=false;

       }

  }

}

Visual force Page:

<apex:page controller="Wrapharsh" sidebar="false" >

   

 <!--VF PAGE BLOCK-->

 <apex:form >

     <apex:pageBlock >

        <apex:pageBlockButtons >

          <apex:commandButton action="{!ProcessSelected}" value="Show Selected accounts" reRender="block2"/>

        </apex:pageBlockButtons>

       <apex:pageBlockSection columns="2">

         <apex:pageBlockTable value="{!wrapaccountList}" var="waccl">

            

           <apex:column >

             <apex:facet name="header">

               <apex:inputCheckbox />

             </apex:facet>

            <apex:inputCheckbox value="{!waccl.isSelected}" id="InputId"/>

           </apex:column>

            

            <apex:column value="{!waccl.accn.name}"/>

            <apex:column value="{!waccl.accn.phone}"/>

            <apex:column value="{!waccl.accn.billingcity}"/>

         </apex:pageBlockTable>

         

          <apex:pageBlockTable value="{!selectedAccounts}" var="sa" id="block2">

            <apex:column value="{!sa.name}"/>

            <apex:column value="{!sa.phone}"/>

            <apex:column value="{!sa.billingcity}"/>

           </apex:pageBlockTable>

       

       </apex:pageBlockSection>

     </apex:pageBlock>

   </apex:form>

</apex:page>