Ruby inject with initial being a hash

Question

Can any one tell me why the following:

[\'a\', \'b\'].inject({}) {|m,e| m[e] = e }

throws the error:

IndexError: string no         


        

Answer 1

Rather than using inject, you should look into Enumerable#each_with_object.

Where inject requires you to return the object being accumulated into, each_with_object does it automatically.

From the docs:

Iterates the given block for each element with an arbitrary object given, and returns the initially given object.

If no block is given, returns an enumerator.

e.g.:

evens = (1..10).each_with_object([]) {|i, a| a << i*2 }
#=> [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

So, closer to your question:

[1] pry(main)> %w[a b].each_with_object({}) { |e,m| m[e] = e }
=> {"a"=>"a", "b"=>"b"}

Notice that inject and each_with_object reverse the order of the yielded parameters.