Ruby Rails - Mapping Json to Model

Question

I'm currently trying to sync my database up with another database with Json, but I'm running into issues with a key they're using.

def sync
    url = '...' # Returns "{ "class": 20, "user": "John" }"
    uri = URI(url)
    response = Net::HTTP.get(uri)
    response_hash = JSON.parse(response)
...

They use the keyword 'class' in their response, but I don't think I'm allowed that, so I have mine as 'cls'. Now, if I try to create a new User, I'll get an error because it cannot map 'class' to anything.

I've been trying to change the key to match my new key, but have been unable to get that to work.

Using answers such as has no effect for some reason.

pattern = { "class" => "cls" }

response_hash.inject({}) do |new_hash, (k, v)|
  key = pattern[k] || k
  new_hash[key] = v
  new_hash
end

But I did notice that I have a Hash, whereas some of the examples created a HashWithIndifferentAccess, so they could do response_hash[:class], but mine would only return nil.

What would be the best solution for this problem? Ideally, I wouldn't have to remap any keys, and could just throw the Json into my database.

Thanks for your help.

bitsapien · Accepted Answer · 2017-05-16 03:33:49Z

2

Simply do this

response_hash['cls'] = response_hash.delete('class')

The result would be { :cls => 20, :user => "John" } which you may directly throw into your database.

edited May 16, 2017 at 3:33

answered May 16, 2017 at 2:06

bitsapien

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5 Comments

advice Over a year ago

I tried what you've suggested, but it's still giving me the same results. I'm unsure why. 'cls' is not there, and 'class' still is. Oh, but I tried with creating a HashWithIndifferentAccess from response_hash, then calling that, and that works.

advice Over a year ago

Small question, if I wanted a nested Object, how would I do that? Say the 'response' contains an Object, and I want to map that to a Model. Passing the hash fails because it expects a Model, but trying to create it early fails because it requires the parent to be created.

bitsapien Over a year ago

Try using accepts_nested_attributes_for. See this answer for reference : stackoverflow.com/a/23674227/755421

advice Over a year ago

I tried adding that, but still get the same issue. MyObject expected, got Hash

bitsapien Over a year ago

You'll have to do a lot more than just adding that statement. Read the answer to get a complete sense of how accepts_nested_attributes_for works.

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