What do these lines on a controller extension mean?

Question

I'm trying to build a test class for a controller extension on a Visualforce page and I need a more in depth description of what certain lines mean. Help on this would be appreciated.

1)

 String msg=e.getMessage();
 integer pos;

 // if its field validation, this will be added to the messages by default
 if (-1==(pos=msg.indexOf('FIELD_CUSTOM_VALIDATION_EXCEPTION, ')))
 {
     ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, msg));
 }

 result=false;

2)

 pr.setRedirect(true);

3) The null here

public void newSkid()
{
   if (updateSkids())
   {
      Skid__c skid=new Skid__c(Name=newSkidName, Dimension__c=newSkidDimension, Number_of_Pieces__c=newSkidNumberofPieces, UOM__c=newskiduom, Weight__c=newskidweight, Bill_of_Lading__c=getBillofLading().id);
      insert skid;

      newSkidName=null;
      newSkidDimension=null;
      newSkidNumberofPieces=null;
      newskidbilloflading=null; 
      newskiduom=null;
      newskidweight=null;
      skids=null;

4) The null!= here

public void deleteSkid()
{
   if (updateSkids())
   {
      if (null!=chosenskidId)
      {
         Skid__c skid=new Skid__c(Id=chosenskidId);
          delete skid;

          skids=null;
          chosenskidId=null;
      }
   }
}

5) The null statement again here

public List<Skid__c> getSkids()
{
   if ( (null!=getBillofLading().id) && (skids == null) )
   {
       skids=[SELECT Id, Name, Bill_of_Lading__c,  
                    Dimension__c, Number_of_Pieces__c, UOM__c, Weight__c
                    FROM Skid__c 
                    WHERE Id =: getBillofLading().id
                    ORDER BY CreatedDate];

6) These functions

public String getChooserender() {
  if (ApexPages.currentPage().getParameters().get('p') != null)
    return 'pdf';
  else
    return null;
}

public PageReference deliverAsPDF() {
  PageReference pdf =  Page.Billofladingtest05222013;
  pdf.getParameters().put('p','p');
  return pdf;
}

Answer 1

When trying to understand some new programming concepts or the specifics of a new language or API, the documentation is invaluable. Here's a couple of resources for you.

• Force.com Apex Code Developer's Guide
• Visualforce Developer’s Guide

Here are some details about the specific code snippets you had questions about.

1) Check out the Exception documentation for e.getMessage();, String Methods documentation for indexOf(), and ApexPages documentation.

 String msg=e.getMessage(); // get the error message
 integer pos;

 // if its field validation, this will be added to the messages by default
 if (-1==(pos=msg.indexOf('FIELD_CUSTOM_VALIDATION_EXCEPTION, ')))
 {
     ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, msg));
 }

 result=false;

2) PageReference documentation

 pr.setRedirect(true);

3) The null here is assigning "no value" (or a blank value) to all of those variables. I'm not entirely sure what that's doing. It could be resetting the values so that they can be used to insert another skid__c.

public void newSkid()
{
   if (updateSkids())
   {
      Skid__c skid=new Skid__c(Name=newSkidName, Dimension__c=newSkidDimension, Number_of_Pieces__c=newSkidNumberofPieces, UOM__c=newskiduom, Weight__c=newskidweight, Bill_of_Lading__c=getBillofLading().id);
      insert skid;

      newSkidName=null;
      newSkidDimension=null;
      newSkidNumberofPieces=null;
      newskidbilloflading=null; 
      newskiduom=null;
      newskidweight=null;
      skids=null;

4) The comparison with null!= here is checking to see if the chosenskidId has a value. It might be better understood as if(chosenskidId != null) which is an equivalent statement.

public void deleteSkid()
{
   if (updateSkids())
   {
      if (null!=chosenskidId)
      {
         Skid__c skid=new Skid__c(Id=chosenskidId);
          delete skid;

          skids=null;
          chosenskidId=null;
      }
   }
}

5) The null statement again here is basically saying: If the resulting sObject (or variable) Id from the function, getBillofLading(), has a value and skids is does not have a value, do the following statements between the brackets { and }.

public List<Skid__c> getSkids()
{
   if ( (null!=getBillofLading().id) && (skids == null) )
   {
       skids=[SELECT Id, Name, Bill_of_Lading__c,  
                    Dimension__c, Number_of_Pieces__c, UOM__c, Weight__c
                    FROM Skid__c 
                    WHERE Id =: getBillofLading().id
                    ORDER BY CreatedDate];

6) See the inline comments for these functions. Also, check out the ApexPages documentation and the PageReference documentation.

public String getChooserender() {
  // if the current page has a 'p' QueryString Parameter
  if (ApexPages.currentPage().getParameters().get('p') != null)
    return 'pdf'; // return 'pdf'
  else
    return null;
}

public PageReference deliverAsPDF() {
  // create a new PageReference to the Page named 'Billofladingtest05222013'
  PageReference pdf = Page.Billofladingtest05222013;
  // add the 'p' QueryString Parameter
  pdf.getParameters().put('p','p');
  // return the PageReference
  return pdf;
}