ruby-on-rails,ruby,ruby-on-rails-4,activerecord , Make instance variable accessible through hash in Ruby


Make instance variable accessible through hash in Ruby

Question:

Tag: ruby-on-rails,ruby,ruby-on-rails-4,activerecord

In Rails, ActiveRecord objects, attributes are accessible via method as well as through Hash. Example:

user = User.first  # Assuming User to be inheriting from ActiveRecord::Base
user.name # Accessing attribute 'name' via method
user[:name] # Attribute 'name' is accessible via hash as well

How to make instance variables accessible through hash for classes not inheriting from ActiveRecord::Base?


Answer:

It's not "through Hash", it's "array access" operator.

To implement it, you need to define methods:

def [](*keys)
  # Define here
end

def []=(*keys, value)
  # Define here
end

Of course, if you won't be using multiple keys to access an element, you're fine with using just key instead of *keys, so that you have not an array of keys (even if only one is given), but just a single key.

Plenty of other classes implement it, namely Structs, so you're free to pick an existing implementation or roll out your own.

Getting instance variables to be affected by these methods means implementing them using instance_variable_get/instance_variable_set. Nothing fancy.


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