Basics of Apex Trigger for beginners

The basic logic of trigger is too huge to cover, I have tried a bit to make everyone understand that how this Apex trigger, a "pain in ass" works, I'll go step by step process of writing apex triggers.

What is Apex Triggers ?

A Trigger is Apex code that executes before or after the following types of operations:

• insert
• update
• delete
• merge
• upsert
• undelete

Types of Apex Triggers

• Before Triggers: Before triggers can be used to update or validate record values before they are saved to the database.
• After Triggers: After triggers can be used to access field values that are set by the database (such as a record's Id or last Updated field), and to affect changes in other records, such as logging into an audit table or firing asynchronous events with a queue.

Example : before insert, after insert, before update, after update, before delete, after delete

Syntax of Trigger

Things to keep in mind while writing apex trigger

• Bulkify your Code : Use Looping through Trigger’s collections variables instead of process through particular indexing.
• All triggers are bulk triggers by default, and can process multiple records at a time.
• Bulk triggers can handle both single record updates and bulk operations like: Data import, Force.com Bulk API calls.
• Bulkify your Code : Use Looping through Trigger’s collections variables instead of process through particular indexing.
• Avoid SOQL Queries or DML statements inside FOR Loops: An individual Apex request gets a maximum of 100 SOQL queries before exceeding that governor limit. 
• Bulkify your Helper Methods: if a trigger uses some Apex methods written in a helper class, it's important that those shared Apex methods are properly designed to handle bulk records. These methods should be written to be invoked with a set of records, especially if the method has a SOQL query or DML operation.

Use @future appropriately:

Here is a list of governor limits specific to the @future annotation:

• No more than 10 method calls per Apex invocation.
• No more than 200 method calls per Salesforce license per 24 hours.
• The parameters specified must be primitive datatypes, arrays of primitive datatypes, or collections of primitive datatypes.
• Methods with the future annotation cannot take sObjects or objects as arguments.
• Methods with the future annotation cannot be used in Visualforce.

Use efficient collection variable of apex triggers

Try using sets and maps to handle bulk record processing.

TRIGGER BEST PRACTICE

• Always use helper class in your trigger, and in helper class perform all your logic. like below

• Don't write more then one trigger on an object, try to add up all your new trigger in a single trigger using different-different helper classes to read more click Order of Execution

There is allot to take care of when writing apex triggers, but I found these to helpful.

Hope this helps 

Happy coding.!!!

Populating Map Using Loops

Many times I faced that I need a Value with its "Group of values".
Getting a unique value in Set is a idea, but what if you have a group of values associated with it.

So that time Map is the best way to settle it down.
we can take Map in many ways but here I am using
Map<String, List<String>>

I used this map allot, because populating this map with Key and Values is a great method.
Here am showing two methods same but in different ways.

Here is the first one.

1:  //Map of Opportunity  
2:    Map<Id, Set<Id>> opportunityMap = new Map<Id, Set<Id>>();  
3:    //Loop through the Opportunity records  
4:    for(Opportunity opp : opportunities) {  
5:      //Check if map key contains System Field  
6:      if(opportunityMap.containsKey(opp.Opportunity_Field__c)) {  
7:       //Get the Values of the Map and add Id to it.  
8:       opportunityMap.get(opp.Opportunity_Field__c).add(opp.Id);  
9:      }else {  
10:       //Creat a new Set at values and add Id to it.  
11:       opportunityMap.put(opp.Opportunity_Field__c, new Set<Id>{opp.Id});   
12:      }  
13:     }  
14:    }  

Here is the same but another way to write it

1:  //Loop through list  
2:  for(Opportunity opp : opportunities) {  
3:    //List of Opportunity  
4:    List<Opportunity> opps = new List<Opportunity>();  
5:   //Check for values of the Map  
6:   &#160 if(mapOpportuinties.containsKey(opp.Fishbowl_Customer_Number__c) == false) {  
7:    //Add to list  
8:    opps.add(opp);  
9:   &#160} else {  
10:     //Add to list  
11:     opps = mapOpportuinties.get(opp.Fishbowl_Customer_Number__c);  
12:     opps.add(opp);  
13:   }  
14:     //Populating map  
15:     mapOpportuinties.put(opp.Fishbowl_Customer_Number__c, opps);  
16:   }  

Using the above snippet every unique value will have a common group of values. its like

Object1 = value1, value2 value3
Object2 = value1, value2, value3
Object3 = value2, value3, value4
Object4 = value5, value6, value7

Cheers....!!!!!

Happy Coding.

Send Email Using Trigger

Here I am using Trigger to send an email to the Contact, which don't have any associated Account.

There is a singleEmailMessage & MassEmailMessageclasses are provided by the Salesforce, which we can use to send an email or email in bulk to the users.

First of all we need to create a Helper class,we will call this class using Trigger, whenever the condition met, the trigger will call this Helper class, and all the stuffs whatever we are doing, will be in helper class. We are using an email template too.

This is an small an easy to understand Example.

Here is the Helper class named "HelperContactTrigger"

/**
* Description : Trigger to send email to the contact if accountId is null .
*
* Created By : Abhi Tripathi
*
* Created Date : 07/16/2013
*
* Revision Logs : V1.0
*
**/
public with sharing class HelperContactTrigger {

//static method
public static List sendEmail(List contacts) {

//query on template object
EmailTemplate et=[Select id from EmailTemplate where name=:'Sales: New Customer Email'];

//list of emails
List emails = new List();

//loop
for(Contact con : contacts){

//check for Account
if(con.AccountId == null && con.Email != null){

//initiallize messaging method
Messaging.SingleEmailMessage singleMail = new Messaging.SingleEmailMessage();

//set object Id
singleMail.setTargetObjectId(con.Id);

//set template Id
singleMail.setTemplateId(et.Id);

//flag to false to stop inserting activity history
singleMail.setSaveAsActivity(false);

//add to the list emails
emails.add(singleMail);
}
}

//send mail
Messaging.sendEmail(emails);

return contacts;
}
}

Now we will call the above class in our trigger named "SendEmailToAccount"
Here is the trigger, just paste this in your Account's Trigger

Trigger SendEmailToAccount on Contact (after insert, after update) {

if(Trigger.isAfter){
if(Trigger.isInsert || Trigger.isUpdate){

//helper class for single email but bulk messages
HelperContactTrigger.sendEmail(trigger.new);
}
}
}

Now you just need to create a Contact record and fill the Email field with your email and save it.
You will receive an email from the your salesforce.

Using Custom Label With Trigger

I have seen many of the developer trying to set custom Error Message on Edit page Layout. So here we can do this using Custom Labels.

Custom Label
Custom labels are custom text values that can be accessed from Apex classes or Visualforce pages.
You can create up to 5,000 custom labels for your organization, and they can be up to 1,000 characters in length.

The purpose of this post is that many time we got a condition to set an error message while writing an Trigger. So here the method to add custom error message on Edit PageLayout

First of all create an Custom Label
Go to
Home --> Setup --> Create --> Custom Labels

The red box or the "Value" field is the error message which is going to be seen by the user on the edit page.

After creating a Custom Label, create a Visualforce page as below which is having an error message

1:  <apex:page >  
2:     <apex:pageMessage severity="info" strength="1" summary="{!$Label.AccountTriggerErrorMessage}"/>  
3:  </apex:page>  

Now add a Trigger on Account Object as below, in this trigger we are adding an error message too.

1:  Trigger TriggerForCustomLabelAccount on Account (before insert, before update) {  
2:  //Check for Event  
3:  if(Trigger.isBefore) {  
4:  //Check for Event Type  
5:  if(Trigger.isInsert || Trigger.isUpdate) {  
6:  //Loop through Account  
7:  for(Account account : Trigger.New) {  
8:  //Check for Account Revenue  
9:  if(account.AnnualRevenue == Null)  
10:  //Here adding error message when condition matches  
11:  account.addError(label.AccountTriggerErrorMessage);  
12:  }  
13:  }  
14:  }  
15:  }  

Now After doing all this, Edit an Account record or create a new one, there will a custom error message on Edit page when condition satisfies.

May the force.com with you, happy coding !!