How to invoke object methods in Pascal

program invokeMethods;
// Declaring a person Object
type Person = object
    // fields to hold data about a person
    private
        person_name : string;
        age : integer;
    // object methods
    public
        // constructor for object instantiation
        constructor init(n : string; a : integer);
        
        // procedures to update data fields
        procedure setName(n : string);
        procedure setAge(a : integer);
        
        // functions to return data field values
        function getName() : string;
        function getAge() : integer;
        
end;
// Defining the object methods
constructor Person.init(n : string; a : integer);
begin
    person_name := n;
    age := a;
end;
procedure Person.setName(n : string);
begin
    person_name := n;
end;
function Person.getName() : string;
begin
    getName := person_name;
end;
procedure Person.setAge(a : integer);
begin
    age := a;
end;
function Person.getAge() : integer;
begin
    getAge := age;
end;
// creating object instance
var
    newPerson : Person;
begin
  // initializing object
  newPerson.init('Alice', 30);
  
  //output object fields  
  writeln('The person''s name is ', newPerson.getName());
  writeln('The person''s age is ', newPerson.getAge());
  
  //setting object fields
  newPerson.setName('Bob');
  newPerson.setAge(20);
  
  //output object fields  
  writeln('The person''s name is ', newPerson.getName());
  writeln('The person''s age is ', newPerson.getAge());
  
end.

Explanation

The Person object holds data about a person’s name and age.

The code defines a constructor that can be invoked to initialize the object with specific values. setName and setAge can update a person’s name and age, respectively. Similarly, the getName and getAge methods return the person’s name and age, respectively. Since all these methods are classified under the public keyword, they are always accessible.

Once the object newPerson is created, the constructor is invoked through the dot operator ( . ) to initialize the values for the name and age to “Alice” and $30$ , respectively. The getName and getAge methods are also invoked through the dot operator to return the field values, which are output accordingly. Since the object declaration does not list any parameters for the getName and getAge functions, no arguments are provided when the method is invoked.

The setName and setAge methods are then invoked to change the values for name and age to “Bob” and $20$ , respectively. The updated values are retrieved and output.

Free AI Mock Interviews

Coding Interview

Coding PatternsFree Interview

Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.

System Design

You TubeFree Interview

Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

How to invoke object methods in Pascal

Example

Explanation