How to Avoid MIXED DML Operation in Salesforce

Problem:

Updating Custom Setting values after user record is created or updated

Custom Setting API Name : ActiveUser__c

Field Name : Name(Standard Field) - It contains profile name
ActiveUsers__c: This field will be updated.

I have add once custom setting value,It contains Name: Customer Portal Manager Custom(Profile Name)

Whenever creating or updating user from above mentioned Profile with the Status Active or Inactive. ActiveUsers__c is the Field will be updated.

You can add multiple profile name in custom setting.

Solution:

To avoid mixed dml operation you need to insert record with @future annotation.

Apex Trigger:

1. trigger usertoActive on User (after insert, after update)
2. {
3.     Set<Id> usrID=new Set<Id>();
4.     Set<Id> ProID=new Set<Id>();
5.    
6.     for(User ur:Trigger.new)
7.     {
8.         usrID.add(ur.Id);
9.         ProID.add(ur.ProfileId);
10.     }
11.     activeUser.userAdd(usrID,ProID);
12. }
13. 
    

Apex Class:

1. global class activeUser
2. {  
3.     @future  
4.     public static void userAdd(Set<Id> userIds,Set<Id> prid)
5.     {
6.         Profile pro=[select Name from Profile where Id=:prid];
7.         List<User> user = [select Id, IsActive from user where Id in:userIds and Profile.Name=:pro.Name];
8.         List<ActiveUser__c> licenseUpdate=[select ActiveUsers__c  from ActiveUser__c where Name=:pro.Name];
9.        
10.         for (ActiveUser__c au: licenseUpdate)
11.         {
12.             for(User ur:user)
13.             {
14.                 if(ur.IsActive)
15.                 {
16.                     au.ActiveUsers__c=au.ActiveUsers__c+1;
17.                 }
18.                 else
19.                 {
20.                     au.ActiveUsers__c=au.ActiveUsers__c-1;
21.                 }
22.                
23.             }
24.         }
25.        
26.         update licenseUpdate;
27.        
28.     }
29. }

Reference: Mixed DML