Interview Question

Explain few considerations for @Future annotation in Apex.

Ans :

• Method must be static
• Cannot return anything ( Only Void )
• To test @future methods, you should use startTest and stopTest to make it synchromouse inside Test class.
• Parameter to @future method can only be primitive or collection of primitive data type.
• Cannot be used inside VF in Constructor, Set or Get methods.
• @future method cannot call other @future method.

Explain Considerations for Static keyword in Apex.

Ans :

• Apex classes cannot be static.
• Static allowed only in outer class.
• Static variables not transferred as a part of View State.
• Static variables and static block runs in order in which they are written in class.
• Static variables are static only in scope of request.

What is difference between public and global class in Apex ?
Ans :

• Public class can be accessed within application or namespace. This is not exactly like public modifier in Java.
• Global class visible everywhere , any application or namespace. WebService must be declared as Global and which can be accessed inside Javascript also. It is like public modifier in Java.

How can you call Apex class using Javascript ? Give Example.
Ans :

1	global class myClass {
2	webService static Id makeContact (String lastName, Account a) {

3	Contact c = new Contact(LastName = lastName, AccountId = a.Id);
4	return c.id;

5	}
6	}

we can execute above method from javascript like :

1	var account = sforce.sObject("Account");
2	var id = sforce.apex.execute("myClass“ , "makeContact",

3	{lastName:"Smith", a:account});

To call a webService method with no parameters, use {} as the third parameter forsforce.apex.execute .

Also, you can use the following line to display a popup window with debugging information:
sforce.debug.trace=true;

What are few Considerations about Trigger ?
Ans :

• upsert triggers fire both before and after insert or before and after update triggers as appropriate.
• merge triggers fire both before and after delete triggers for the losing records and before update triggers for the winning record only.
• Triggers that execute after a record has been undeleted only work with specific objects.
• Field history is not recorded until the end of a trigger. If you query field history in a trigger, you will not see any history for the current transaction.
• You can only use the webService keyword in a trigger when it is in a method defined as asynchronous; that is, when the method is defined with the @future keyword.
• A trigger invoked by an insert, delete, or update of a recurring event or recurring taskresults in a runtime error when the trigger is called in bulk from the Force.com API.
• Merge trigger doesn’t fire there own trigger instead they fire delete and update of loosing and winning records respectively.

Which SOQL statement can be used to get all records even from recycle bin or Achieved Activities?
Ans : We will need “ALL Rows” clause of SOQL.
Sample :

1	SELECT COUNT() FROM Contact WHERE AccountId = a.Id ALL ROWS

---

 How can you lock record using SOQL so that it cannot be modified by other user.

Ans : we will need “FOR UPDATE” clause of SOQL.
Sample :

1	Account [] accts = [SELECT Id FROM Account LIMIT 2 FOR UPDATE];