I have been customising the Lookup for contacts : I have a constraint of populating contacts for an account which is chosen on my page. My page is as follows : This directly belongs to the class2: <apex:outputLabel for="Account Name" style="text-align:left;">Account Name</apex:outputLabel>&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; <apex:inputfield id="acclookup" value="{!cObj.AccountName__c}"/> <apex:commandButton value="ok" action="{!accountsel}" rerender="false"/> -------------- All the Backend processing is taking place in class1 and values are returned to class2 ----------------------- fObj is an instance of class1 which is instantiated on click of above 'ok' Command button. <apex:inputText id="theLookupText" value="{!fObj.assignvalue}"/>

IN THE INPUT HIDDEN I AM SAVING THE ID RETURNED FROM THE CLASS1 STOREVALUE METHOD

<apex:inputHidden id="CentralContactField" value="{!fObj.rObj.Central_Contact__c}"/> <apex:commandLink action="{!fObj.refreshlist}" rerender="searchPanel,theText,tblConts"> <apex:image id="lookupabc" url="{!$Resource.SearchImage2}" height="25" width="25" onclick="openpopUpwindow('{!$Component.lookupPanel}','{!$Component.lookup}')"/> </apex:commandLink> <!-- popup for lookupIcon--> <apex:outputPanel id="outerPanel"> <apex:outputPanel id="lookupPanel" style="background-color:White; border:1px solid black; width:600px; display:none;"> <apex:actionRegion > <apex:outputLabel ><b>Search</b></apex:outputlabel>&nbsp;&nbsp; <apex:inputText id="theText" value="{!fObj.search}" onkeypress="return handleKeyPress(event,'{!$Component.btn}');"/> <apex:commandbutton id="btn" value="Go!" action="{!fObj.go}" rerender="searchPanel"/>&nbsp; <apex:commandbutton value="New" action="{!fObj.new1}" rerender="searchPanel"/> <apex:commandButton id="cancelBtn" value="Cancel" onclick="return hidepopupwindow('{!$Component.lookupPanel}')" action="{!fObj.hidehide}"/> <apex:pageBlock id="searchPanel"> <apex:messages /> <apex:pageBlockSection title="Contacts"> <apex:outputPanel rendered="false" rendered="{!fObj.ren}"> <apex:pageBlockTable value="{!fObj.contact}" var="c" id="tblConts"> <apex:column headervalue="name" colspan="2"> Here in the page block table i am having a command link for the name of the contact which is retrieved from the controller class1. On clicking of this link the id is populated into the LOOKup field central_contact__c; <apex:commandLink id="cmdlink" action="{!fObj.storevalue}" value="{!c.Name}" rerender="theText,CentralContactField,theLookupText,theLookupText1" oncomplete="return hidepopupwindow('{!$Component.lookupPanel}')"> <apex:param value="{!c.id}" name="contid"/> <apex:param value="{!c.Name}" name="contName"/> </apex:commandLink> </apex:column> <apex:column headervalue="Email"colspan="2"> <apex:outputText value="{!c.Email}"></apex:outputText> </apex:column> </apex:pageBlockTable> </apex:outputpanel> </apex:pageBlockSection> </apex:pageblock>

The Controller part is as follows :

public class class2{ Public Id accname{get;set;} Public FinalCustomContact fObj{get; set;} public PageReference accountsel() { this.accname = cObj.accountname__c; system.debug('Account Name---:'+ cObj.accountname__c); /*Instantiating the class1 reference*/ -------here the parameterised constructor is invoked------------ fObj = new FinalCustomContact(cObj.accountname__c); return null; } ---------------IN CLASS2 I NEED TO SAVE THE VALUES RETURNED FROM CLASS ONE IN THE BACKEND FIELDS USING FOLLOWING METHOD-------------- Public void Conts() { -----------HERE i reference the value to be stored in the Centrel_Contact__C lookup---------- --------------HERE THE INVALID STRING ERROR IS THROWN REFERENCING TO fObj.rObj.Central_Contact__c!='' COMPARISION---------- ----------WHEN I CHECK IT PASSES ID ONLY AND NOT A STRING....---------- if(fObj!=null && fObj.rObj != null && fObj.rObj.Central_Contact__c!=''&&fObj.rObj.Central_Contact__c!= null){ cObj.Central_Contact__c = fObj.rObj.Central_Contact__c; } else{ cObj.Central_Contact__c = null; } } }

THE PROCESSING IS TAKING PLACE IN CLASS1 AS FOLLOWS:

Public class Class1 { public List<contact> contact{get; set;} Public Id accname; Public String textfieldid; Public String varname; Public String newContact{public get; public set;} public FinalCustomContact() { newContact = ''; Id id = ApexPages.currentpage().getParameters().get('id'); rObj = (id == null) ? new caps__c():[SELECT accountname__c,name,central_contact__c from caps__c where Id=:id]; num = ApexPages.currentPage().getParameters().get('num'); contact = new List<contact>(); ren = true; ren1 = false; ren2 = false; this.varname = null; this.idid = null; } ------------------------HERE ONCE THE ACCOUNT IS CHOSEN IN THE PAGE AND THE ACCOUNTSEL METHOD IS RUN IN CLASS2 THIS CONSTRUCTOR GETS INVOKED----------- public FinalCustomContact(Id acc) { newContact = ''; Id id = ApexPages.currentpage().getParameters().get('id'); rObj = (id == null) ? new caps__c():[SELECT accountname__c,name,central_contact__c from caps__c where id=:id]; num = ApexPages.currentPage().getParameters().get('num'); contact = new List<contact>(); this.accname = acc; contact = [Select id,Name,LastName,Email from contact where contact.Account.id = :acc]; this.varname = null; this.idid = null; if(contact.size()==0){ msg1='No records were found based on your criteria'; } else{ } -------------THIS IS DISPLAYED AS NULL SINCE ITS AN ID AND NOT A STRING------------------------------ system.debug('--------------'+rObj.Central_Contact__c); } /*Returning the Search Results to Table*/ public List<contact> getcontact(){ return contact; } Public id getaccname(){ return accname; } Public void setaccname(Id acc){ this.accname = acc; } Public Id giveawayid; Public Id idid; Public Id getdisplay(){ return giveawayid; } --------THIS METHOD RUNS WHEN THE COMMAND LINKED NAME IS CHOSEN TO POPULATE VALUE IN LOOK UP---------- public void storevalue() { giveawayid = ApexPages.currentPage().getParameters().get('contid'); search = ApexPages.currentpage().getParameters().get('contName'); system.debug('ID-----------------------'+giveawayid); newContact = giveawayid; system.debug('NewCONTACT-----------------------'+newContact); this.varname = search; this.idid = giveawayid; ---------HERE THE IS IS BEING ASSIGNED TO THE LOOKUP FIELD WHICH IS LATER REFERENCED IN CLASS2------------ rObj.Central_Contact__c = giveawayid; } public Id getididid(){ return idid; } public void setididid(Id srch){ this.idid=srch; } Public String getassignvalue(){ return varname; } Public void setassignvalue(String name){ this.varname = name; } } THE PROBLEM ARISES WHEN A VALUE IS NOT CHOSEN FROM THE LOOK UP AND I RUN THE VOID CONTS METHOD FROM CLASS2 WHICH IN TURN TRIES TO CHECK IF ID IS NOT NULL , BUT UNFORTUNATELY IT THROWS ERROR SAYING IT AS INVALID ID.... COULD YOU PLEASE HELP ME FINDOUT WHY THIS IS ARISING , FOR THE BEST OF MY KNOWLEDGE IM NOT EXPLICITLY ASSIGNING ANY VALUE WHEN THE CONTACT IS NOT CHOSEN FROM THE LOOKUP AT THAT TIME HOW DO I REFERENCE THE VALUE FROM THE CLASS1 ?