Question

I accidentally created following check, that works fine, but I’m curious why 🙂

1. First of all, I know I can assign :a instead of ‘a’ 😉
2. I know the right formula for this check, I’m just curious why this works
3. I don’t care about optimizing this (read 2)

if params['a'] < 0 || params['a'] > params['b || params[:b] < 1]

Why this works, if there is no closing after ['b.

Apart from this everything works fine, until I remove last ], or change it to something else.

UPDATE:

Here is output from ruby:

irb> params

 => {"a"=>3, "id2"=>"2", "b"=>2, "id"=>"1", :id=>"2"}

irb> if params['a'] < 0 || params['a'] > params['b' || params[:b] < 1]
irb>   puts 'strange...'
irb> end

strange...

=> nil

Answer 1

Well, it certainly looks like you have an open quote which gets closed somewhere else, later down the road, on some other line.

Fun fact:

ruby_hash = {}
ruby_hash['class Atom
def initialize
end
end'] = 0

Works. Because it’s just a string key. So you’re just evaluating a huge long string as a key to to the ‘params’ hash which is most certainly going to evaluate to nil because it’s not an existing key in the hash.

---

Edit!
You edited the question and gave more information. Let’s break this down.

params = {"a"=>3, "id2"=>"2", "b"=>2, "id"=>"1", :id=>"2"}
# Simple enough, nothing strange here.
if params['a'] < 0 || params['a'] > params['b' || params[:b] < 1]
    puts 'strange...'
end
The plot thickens, or does it?

If!

params['a'] < 0

That means, of course: if the value of ” a ” in params is less than 0

|| 

… That means ‘or’

params['a'] >

Stopping here for a sec – if the value of ‘a’ is greater than….

params['b' || params[:b] < 1]

Wait, what? Let’s look deeper.

params[ => We look inside the hash
'b' || params[:b] < 1 ## HERE IS THE 'MAGIC' => 'b' || params[:b] < 1
] # end of the key

So the magic is :
We want the result of the OR statement between :

• the string ‘b’
• the evaluation of ‘params[:b] < 1

So what is really happening? Well, in truth, since ‘b’ is not false, it will just return the value of params[‘b’], so this is what your if statement really is:

if params['a'] < 0 || params['a'] > params['b']

If ‘b’ evaluated to false for whatever reason, you would end up with “params[params[b:] < 1]” which in your case would be false and would then means “params[false].

Does this make sense?