How to check accessibility of an user on a particular record ?

It is a very challenging requirement, Generally we will update records through trigger for complex requirement.
 Lets think a scenario where we have to update a particular field value(say field name-IsUpdate) on an Opportunity and few profile is having editable access to that field,there is a already a trigger written for other purpose(updating some other thing) on Opportunity,So we have to modify same trigger and add our logic in that trigger.
Our first and foremost approach  would be checking profile name in the condition as below.

Approach-1(Using profile)

Assume that profile "Test_profile_name" is having editable access to that field(IsUpdate)
Profile ProfileName = [select Name from profile where id = :userinfo.getProfileId()];
for(Opportunity opp:trigger.new){

     if(profileName.Name.containsIgnoreCase('Test_profile_name')){
   
          // opp.IsUpdate = true;
     }
}

It will work fine no doubt, But let assume we have more than 100 profiles having editable access then we have add each profile name in same condition separated by OR.

if(profileName.Name.containsIgnoreCase('Test_profile_name') OR profileName.Name.containsIgnoreCase('Test_profile_name')...................)

What if profile name is renamed or deleted then also it wont work. So finally above approach is not good at all.

Approach-2(Enforcing Object and Field Permissions)

We can avoid above issue by using sobject describe result method.

if (Schema.sObjectType.Opportunity.fields.IsUpdate.isUpdateable()) {
   // Update Opportunity IsUpdate
}

This approach is 90% right still some problem is there, By this approach we can check object level access but what about record level access ? As we are dealing with record(updating record) we have to check record level accessibility.

It is quite often that one user may have object level edit access still he/she cant edit particular record.

Approach-3(Using UserRecordAccess object).

You can write query to fetch user access to a record 

UserRecordAccess  = [SELECT RecordId, HasReadAccess, HasTransferAccess, MaxAccessLevel
                     FROM UserRecordAccess
                     WHERE UserId = [single ID]
                     AND RecordId = [single ID]

or 

SELECT Id, Name, UserRecordAccess.HasReadAccess, UserRecordAccess.HasTransferAccess, UserRecordAccess.MaxAccessLevel 
      FROM Opportunity

for more details 

https://www.salesforce.com/developer/docs/api/Content/sforce_api_objects_userrecordaccess.htm

How to call apex class from process builder?

As we all know it is not possible to invoke apex class from work flow,for that purpose sfdc lunched new functionality called process builder.

Please go through this link. In my previous post i have explained about creation of process builder and updating a field through process builder.

http://salesforceworld4u.blogspot.in/2015/04/updating-records-thorough-lightening.html

Now this is post is all about calling an apex class from process builder.

public class DeleteBrassCaseUtil{

  @InvocableMethod(label='Get Brass Cases Names' description='Returns the list of Brass Cases corresponding to the specified Brass Cases IDs.')
  public static void deleteBrassCase(List<Id> BrassCaseIds)
    {
        List<BRASS_Case__c> brassCases =[SELECT Id,Is_Org_Case_Created__c FROM BRASS_Case__c WHERE Is_Org_Case_Created__c =true AND id IN :BrassCaseIds];
 
        delete brassCases;
    }
}

The annotation "@InvocableMethod" defines this method can be invoked from process builder. This class will delete some custom object records based on meeting criteria.

Below is the process builder.

How to get salesforce instance url in apex class?

This is quite simple to get but some developer used to hard code that instance url, Actually we should not hard code url like "https://cs12.salesforce.com" because it differs from org to org.

Use below code to get instance url in apex class dynamically.

String baseUrl = URL.getSalesforceBaseUrl().toExternalForm();