APEX : CONSTRUCTOR
Constructor
The constructor is a special method which has the following properties :
For Example :
- Method name will be the same as a class.
- Access specifier will be public.
- This method will be invoked only once that is at the time of creating an object.
- This is used to instantiate the data members of the class.
For Example :
=================================================
public class TestObject
{
\\The no argument constructor
public TestObject()
{
\\code
}
}
=================================================
There are 3 types of constructors:
- 1. Default Constructor
- 2. Non-parameterized Constructor
- 3. Parameterized Constructor
1. Default Constructor
If an Apex Class doesn't contain any constructor then Apex compiler by default creates a dummy constructor on the name of the class when we create an object for the class.
For Example:
=================================================
public class Example
{
}
Example e = new Example();
=================================================
In the above example, the apex class doesn't contain any constructor. So when we create an object for example class the Apex compiler creates a default constructor.
For Example:
=================================================
public example()
{
}
=================================================
=================================================
public example()
{
}
=================================================
2. Non-parameterized Constructor
- It is a constructor that doesn't have any parameters is called Non-parameterized constructor.
- Parameters are nothing but the values we are passing inside a constructor.
=================================================
public class Example
{
Integer number;
String Name;
public Example() //Non-parametarized Constructor
{
number=10;
name=Salesforcekid;
}
}
=================================================
3. Parameterized Constructor
- It is a constructor that has parameters.
- That means here we will take input from the user and then map it with our variable.
=================================================
public class Example
{
Integer number;
String Name;
public Example(Integer x, String myname) //Parametarized Constructor
{
number = x;
Name = myname;
}
=================================================
Now let's create an apex program to understand the use of constructor in an apex.
- Open developer console by clicking the org name on the Salesforce page.
- Click File --> New --> Apex Class.
- Enter the class name.
- Write the Apex Class.
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public class Employee //Class
{
String EmployeeName;
Integer EmployeeNo;
public Employee() //Constructor
{
EmployeeName = 'Ajinkya';
EmployeeNo = 10;
}
public void show() //Method
{
System.debug('Employee Name is '+ EmployeeName);
System.debug('Employee No is '+ EmployeeNo);
}
}
=================================================
Now open anonymous window and type this
Employee c1 = new Employee();
Employee c2 = new Employee();
c1.show();
c2.show();
=================================================
This will give you the following output
EmployeeName is Ajinkya
EmployeeNo is 10
=================================================
Usage of Apex Program within Visualforce Page
When you want to call Apex class in visualforce page we have to declare our apex class in the following format.
<apex:page Controller="ClassName">
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Whenever we call a visualforce page in which controller attribute is defined it will first create an object for the apex class which is defined in the controller.
You can call it a client-side controller.
When an object is created for the Apex class first it invokes the constructor.
WOHOOO.....You have just completed this Apex: Constructor episode.
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If you like this salesforcekid learning platform please let me know in the Comment section...Also, Share with your salesforce folks wish you
Happy learning ☁️⚡️ (Learn. Help. Share.)
<< PREVIOUS NEXT >>
APEX : CONSTRUCTOR
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Like u mentioned when we call a Visualforce page it will calls the constructor how to do the same when using Lightning Web components instead of Visualforce.
ReplyDeleteNice Question...We can use render(){} function in LWC.
DeleteThis will help you to achieve this.
I hope this will help you.
⚡️HAPPY LEARNING⚡️
u mean to call the apex class constructor from LWC JS render function.I'll let u know if it works thanks!.
Deletehow to import apex constructor in lwc
ReplyDeleteHey!! In LWC we use following syntax to import Methods in JavaScript file as :
Deleteimport apexMethodName from '@salesforce/apex/Namespace.Classname.apexMethodReference';
I hope the above syntax will help you!!
⚡️HAPPY LEARNING ⚡️
What exactly is going on with the c1.show(); command? I'm going to botch this syntax, but is it something like "show(Employee c1);" where the c1 is an input into the show method?
ReplyDeleteIts only calling contractor to display the value inside the constructor.
DeleteHey i am new to programming just want to ask why we need constructor? and what exactly it do in apex? real life scenario example will be better for understanding.
ReplyDeleteThanks !!!