Question

I mean, I don’t declare

my_var = new variable

or something like that.
I just go with

my_var = 1;

Similarly, why can’t I just

books["War and peace"] = :masterpiece

Why I need to define in advance?

books = {}

Answer 1

Doing:

my_var = 1

Is defining and assigning the local variable. With a hash it could be done like this:

books = { 'War and Peace' => :masterpiece }