In  this is post, I have given very simple examples for learning salesforce Apex Triggers concepts.
Apex Triggers saves lots of time involving in automating complex businuess process

Examples


  1. Use case 1:

  • when account is inserted, automatically contact also created for that account.

trigger insertContact on Account (after insert)
{
Contact cont = new Contact();
cont.LastName = Trigger.new[0].name;
cont.AccountId = Trigger.new[0].ID;
insert cont;
}

  • Explanation:

Above one is a simple trigger to insert contact when you create account. the text which is mentioned in green color is trigger name. And text which is mentioned in red color is event name.

Trigger.New is a context variable. which returns a list of new records of the sobjects which we are going to insert into the database.



  1. Use Case 2:

  • Create a trigger on opportunity that throws error if Amount is less than 5000

trigger op_trigger1 on Opportunity (Before Insert, Before Update)
{
    for(Opportunity a : Trigger.New)
{
    if(a.Amount < 5000)
   a.addError('Amount can not be less then 5k');
}
}
  • Explanation:

Above one is a simple trigger which fires if Opportunity values is less than 5000 k. This is trigger triggers every time when record is created and updated


  1. Use Case 3:

  • If a New record is created, Amount should not be less than 5k If an Existing record is being updated , Amount should not be less than 3k

trigger opp_trigger2 on Opportunity (Before Insert, Before Update)
{
   for(Opportunity a : Trigger.New)
{
   if(Trigger.isInsert && a.Amount < 5000)
   a.addError('Amount can not be less than 5k');
   else if(Trigger.isUpdate && a.Amount < 3000)
   a.addError('Amount can not be less than 3k');
    }
}


4. Use Case 4:

  • Create a contact record on New Opportunity Insert
trigger opp_trigger3 on Opportunity (After Insert)
{
    Contact c = new Contact();
   for(Opportunity o : Trigger.New)
{
   c.AccountID = o.AccountID;
   c.FirstName = 'Oppertunity';
   c.LastName = 'Owner';
   insert c;
   }
}





Introduction to Triggers:
Apex Trigger is an action which gets fired on the particular event. In salesforce trigger is apex code that executes before or after the below types of operations.
  • Insert
  • Update
  • Delete
  • Undelete
Triggers will run before object records are inserted, updated, deleted into the database or after records are inserted, updated, deleted and restored.
  1. Apex Triggers can be classified into two types:
    1. Before triggers can be used to update or validate record values before they are saved to the database.
    2. After triggers can be used to access field values that are set by the database, and to effect changes in other records.
  1. Events in triggers:
    1. Before Insert, Before Update, Before Delete
    2. After Insert, After Update, After delete, After Undelete

  1. When to use “before” vs “after” triggers:






  1. Syntax to create sample trigger:
    1. Use below syntax to create trigger.
      1. trigger on ObjectName (<events>){
// Code Goes Here :)
}

  1. Trigger Context Variables:
    1. All triggers define implicit variables that allow users to access run time context. These variables are contained in the System.trigger class.
      1. Trigger.New
      2. Trigger.old
      3. Trigger.NewMap
      4. Trigger.OldMap
      5. Trigger.isAfter
      6. Trigger.isBefore
      7. Trigger.isInsert
      8. Trigger.isUpdate
      9. Trigger.isDelete
      10. Trigger.isUndelete.
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