Symbolize keys in MySQL JSON fields using ActiveRecord - mysql

Question

I have a JSON column in one of my models, that holds an array of hashes
create_table "articles", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
t.string "title"
t.json "data"
end
When I store a Ruby hash inside #data, ActiveRecords takes care of converting it to json and storing it in the DB.
article = Article.new(data: [{ some: "data" }])
article.save
article.reload.data
=> [{ "some" => "data" }]
But as you can see in the example above, when I read the field back from the DB, the keys are converted to strings (this is obvious because it's stored as JSON).
My question is: Does ActiveRecord provide any built-in functionality to convert the string keys to symbols?
I could overwrite the getter and symbolize the keys inplace, but this becomes unhandy if you have a lot of json fields:
def data
_data = self[:data]
_data.each.with_index do |hash, idx|
_data[idx] = hash.symbolize_keys
end
_data
end
It becomes more messy when you have mixed data types inside the same array and you have to take care if it is a hash or not...
# this would fail because String does not implement #symbolize_keys
article.data << "foo"
article.data << { bar: "test" }

Answer 1

There is a way to convert the string keys to symbols, if it is a valid hash.
JSON.parse(article.reload.data,:symbolize_names => true)
This method will symbolize all keys recursively. It wont preserve any mixing of symbol and string.
But in your case if you have missed data types you also need to check whether the element of the array is a hash or string. You might try this using Kernel#eval :
def valid_hash?(string)
eval(string).is_a?(Hash)
rescue SyntaxError
false
end
More details for eval method is here