Question

Hey guys so I’m trying to construct some json based on a form submission. My json needs to be something like this (truncated for simplicity):

{"id":0,"creditCard":{"address":{"state":"AZ"}}}

Basically I’m trying to do it like this:

json_hash = Hash.new
json_hash["id"] = 0
json_hash["creditCard"]["address"]["state"] = "test"
json_hash.to_json

But its throwing this errror:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]

At the 3rd line in the example given (the deeply nested thing). Do ruby hashes work like this? Or are there extra steps I need to take?

Answer 1

Because at the third line you’re evaluating a json_hash['creditCard'] which is nil, then it has no method [].

You can build an hash like that using

json_hash = { "id" => 0,"creditCard" => { "address" => {"state" => "AZ"}}}

and it has the given format.

Thats a short syntax, to specify the fact that what you want in json_hash it’s NOT a single hash. It is an hash which has the value 0 in its "id" key, then in its "creditCard" it stores another hash which contains another hash (i.e. {"state" => "AZ"}) in its "address" key.

Look at this pry transcript:

pry(main)> json_hash = { "id" => 0,"creditCard" => { "address" => {"state" => "AZ"}}}
=> {"id"=>0, "creditCard"=>{"address"=>{"state"=>"AZ"}}}
pry(main)> json_hash.object_id
=> 2175368520
pry(main)> json_hash['creditCard'].object_id
=> 2175368560
pry(main)> json_hash['creditCard']['address'].object_id
=> 2175368600

all these values have different object_id so they are not the same thing, neither property of the same thing.