Apex Interview Question – Salesforce – Part 16

151. Give Sample Code Snippet of Apex that that will show that how Parent and Child record can be inserted in Single Statement ?
Ans : It can be done with help of External Id.

1	Date dt = Date.today().addDays(7);

2	Opportunity newOpportunity = new Opportunity(Name = 'shivasoft', StageName = 'Prospecting', CloseDate = dt);

3

4

/*

5	Create the parent reference. Used only for foreign key reference  and doesn't contain any other fields. If we provide any other value it will give following error

6

7	System.DmlException: Insert failed. First exception on row 1; first error: INVALID_FIELD, More than 1 field provided in an external foreign key reference in entity: Account: []

8

*/

9

10	Account accountReference = new Account(MyExtID__c = 'SHIVA1234567');

11	newOpportunity.Account = accountReference;

12

13	//  Create the Account object to insert.  Same as above but has Name field.  Used for the insert.

14	Account parentAccount = new Account(Name = 'Shiva', MyExtID__c = 'SHIVA1234567');

15

16	Database.SaveResult[]

17	results = Database.insert(new SObject[] {  parentAccount, newOpportunity });

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152 . 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

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153. 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];

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154. If you set more than one savepoint, then roll back to a savepoint that is not the last savepoint you generated, What will happen to later savepoint variables ?
Ans : if you generated savepoint SP1 first, savepoint SP2 after that, and then you rolled back to SP1, the variable SP2 would no longer be valid. You will receive a runtime error if you try to use it.

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155. What are few limitations (points to remember) of Savepoint or Transaction Control in Apex ?
Ans :

• Each savepoint you set counts against the governor limit for DML statements.
• Static variables are not reverted during a rollback. If you try to run the trigger again, the static variables retain the values from the first run.
• Each rollback counts against the governor limit for DML statements. You will receive a Runtime error if you try to rollback the database additional times.
• The ID on an sObject inserted after setting a savepoint is not cleared after a rollback.

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156. 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 task results 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.

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157. How to execute Apex from Custom button or Javascript ? Give Example.
Ans :

It is possible using Ajax toolkiit.

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	{!REQUIRESCRIPT("/soap/ajax/33.0/connection.js")}

2	{!REQUIRESCRIPT("/soap/ajax/33.0/apex.js")}

3	var account = sforce.sObject("Account");

4	var id = sforce.apex.execute("myClass" , "makeContact",

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

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

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

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158.  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.

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159. 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.

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160. 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.