SQL & PL/SQL

I'm looking for a way to define a data structure in Oracle PL/SQL with heterogeneous data and where I'm able to iterate the values.
My use case is that I receive a bunch of values from a Resource Template and have to process them and insert them in a table.
I would like to have something like this:

DECLARE
   TYPE books IS RECORD
      (title  varchar( 50) := myvar1,
      author  varchar( 50) := myvar2,
      subject varchar(100) := myvar3,
      book_id number       := myvar4);
BEGIN
  FOR item IN ('SELECT * FROM books')
  LOOP
    -- Here I would access each individual item key and value (title, author...)
    my_function(item.key, item.value)
  END LOOP;
END;

Note that in the example above I want to iterate the fields (columns), not records, there's a single record.
So I want something very similar to an object in Javascript:

var obj = {
  title: 'Romeo and Juliet',
  author: 'Some dude',
  subject: 'Romance',
  book_id: 332764
};

for (const prop in obj) {
  console.log(`obj.${prop} = ${obj[prop]}`);
}

This is for Oracle 19c.
Is there a way to achieve this in a simple way?
Note that I'm using RECORD in the example, but it could be something else.
This was also asked in StackOverflow, but there were no answers.