Question

Anyone care to explain why I’m getting an error here:

[~]$ irb
>> h = Hash
=> Hash
>> h["a"] = 100
NoMethodError: undefined method `[]=' for Hash:Class
from (irb):2

but not here:

>> h = {'dog' => 'canine'}
=> {"dog"=>"canine"}
>> h["a"] = 100
=> 100

Answer 1

You need to call Hash.new. With your code you are assigning the Hash class to h, not an instance of it.

irb(main):001:0> h = Hash
=> Hash
irb(main):002:0> h.class.name
=> "Class"
irb(main):003:0> h = Hash.new
=> {}
irb(main):004:0> h.class.name
=> "Hash"