Question

I have a class that extends Hash, and I want to track when a hash key is modified.

What’s the right syntax to override the [key]= syntactic method to accomplish this? I want to insert my code, then call the parent method.

Is this possible with the C methods? I see from the docs that the underlying method is

rb_hash_aset(VALUE hash, VALUE key, VALUE val)

How does that get assigned to the bracket syntax?

Answer 1

The method signature is def []=(key, val), and super to call the parent method. Here’s a full example:

class MyHash < Hash
  def []=(key,val)
    printf("key: %s, val: %s\n", key, val)
    super(key,val)
  end
end

x = MyHash.new

x['a'] = 'hello'
x['b'] = 'world'

p x