before and After triggers

befor Update Triggers
=======================================================================
 
 1.On  the records which are Trigger.New in before Update

   Trigger.New
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes Yes No No

 2.On  the records which are Trigger.NewMap in before Update

   Trigger.NewMap
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes Yes No No

 3.On  the records which are Trigger.old in before Update

   Trigger.old
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No Yes No


 4. On  the records which are Trigger.oldMap in before Update

   Trigger.oldMap
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No Yes No

===============================================================
after Update Trigger
================================================================

 1.On  the records which are Trigger.New in after Update

   Trigger.New
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No Yes Yes


 2. On  the records which are Trigger.NewMap in after Update

   Trigger.NewMap
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No Yes Yes

 3.On  the records which are Trigger.old in after Update

   Trigger.old
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No No No


 4. On  the records which are Trigger.oldMap in after Update

   Trigger.oldMap
  ------------------------------
    Read Write SOQL DML
  -------------------------------
    Yes No No No
Basic Scenario:

 1. Object : Account 
    Fields : Phone

 2. Object : Contact 
    Field  : Account(Lookup)
          MobilePhone

Scenario 6: When ever the  Account' object phone no is modified ,Its corresponding child 
     contacts records mobilePhone values should be replaced with
     Account's New phoneNo

Trigger :
----------
trigger Scenario6 on Account (before update) {
 List<Account> oldList=[select  id,phone,(select mobilephone from Contacts) from Account where id In: Trigger.Old];
    List<Contact> cons=new List<Contact>();
    for(Account a:oldList){
        for(Contact c:a.contacts){
          c.MobilePhone=Trigger.newMap.get(a.id).Phone;
            cons.add(c);
        } 
    }
    update cons;
}

TestClass :
-----------
@isTest
private class scenario6 {
 @isTest
    static void testme(){
        Account a=new Account(Name='aaa',phone='111');
        insert a;
        Contact c1=new Contact(lastname='test',mobilePhone='111',accountid=a.id);
        insert c1;
        a.phone='123';
        try{
            update a;
        }catch(Exception e){
            System.debug(e);
        }
        Account acc=[select id ,phone from Account where id=:a.id];
        Contact con=[select id,mobilePhone from Contact where Id=:c1.id];
        System.assertEquals(acc.phone,'123');
        System.assertEquals(con.MobilePhone,'123');
    }
}

Scenario 7: 

Object  : Account 

Fields  :Manager : Text (Create this custom Field first)

 : Industry : PickList( Standard Field)

Object : User

Fields : Account_Manager : Text Fields

Task : When ever the industry field value is modified as banking then 
  
 1.Fetch the user who is the owner of the Account Record

 2.Update the Account_Manager field on the user with Manager field value

Trigger:

trigger Scenario7 on Account (before update ) {
    Map<Id,Account> oldMap=Trigger.oldMap;
    Map<Id,Account> newMap=Trigger.newMap;
    List<Id> accs=new List<Id>();
    for(Id aid:oldMap.keySet()){
        if(oldMap.get(aid).Industry !=newMap.get(aid).Industry  && newMap.get(aid).Industry=='Banking'){
           accs.add(aid); 
        }
    }
    List<Id> userids=new List<Id>();
    for(Id mid:accs){
        userids.add(newMap.get(mid).ownerid);
    }
    List<user> newUsers=new List<User>();
    Map<Id,User> userMap=new Map<Id,User>([select id,Account_Manager__c from User where id in :userids]);
     for(Id mid:accs){
        Id uid=newMap.get(mid).ownerid;
        User u=userMap.get(uid);
        u.Account_Manager__c=newMap.get(mid).Manager__c;
         newusers.add(u);
     }
    update  newusers;

}


Scenario 8:
 
 Object : Account 

 Field : Name 
 
 Object : Contact

 1.Before insert
  1.When we are inserting new account record first check if there are
    any duplicate records with same name already existing 
  
  2. if they are existing throw error message

 2.after update :

  1. Check wheather there are any contact records already existing 
     for the give account

  2. if no contacts are existing create new contact 


Trigger Class :

public class TriggerExample {
    public static void beforeInsert(List<Account> accs){
        List<String> names=new List<String>();
        for(Account a:accs){
            names.add(a.name);
        }
        List<Account> duplicates=[select id,name from Account where name in:names];
        if(duplicates.size()>0){
            Set<String> dupnames=new Set<String>();
            for(Account a:duplicates){
                dupNames.add(a.name);
            }
            for(Account ac:accs){
               if(dupNames.contains(ac.Name))
                    ac.addError('Duplicate name Exists');
            }
        }
    }
    public static void afterUpdate(List<Account> accs){
        List<Contact> cons=new List<Contact>();
        List<Account> accounts=[select id,name,phone,(select id from Contacts) from Account where id in:accs];
        for(Account a:accounts){
            if(a.contacts.size()==0){
                Contact c=new Contact();
                c.accountid=a.id;
                c.lastname=a.name;
                c.phone=a.phone;
                cons.add(c);
            }
        }
        insert cons;
    }

}

Trigger:
---------
trigger scenario8 on Account (before insert,after update) {
    if(Trigger.isBefore && Trigger.isInsert){
        TriggerExample.beforeInsert(Trigger.New);
    }
    if(Trigger.isAfter && Trigger.isUpdate){
        TriggerExample.afterUpdate(Trigger.New);
    }
}


Test Class :
@isTest
private class Scenario8 {
    @isTest
    static void testme(){
        Account a1=new Account(Name='aaa');
        insert a1;
        Integer count=[select count() from Account];
        Integer size=[select count() from Contact];
        Account a2=new Account(Name='aaa');
        try{
           insert a2; 
        }Catch(Exception e){
          System.debug(e);  
        }
   Integer newCount=[select count() from Account];
         System.assertEquals(count,newCount);
        a1.phone='123';
        update a1;
        Account acc=[select id,phone from Account where phone='123'];
        System.assertEquals(acc.phone,'123');
        Integer newSize=[select count() from Contact];
        System.assertEquals(size+1,newSize);
        
    }

}