adamcooke / apiable-model-errors

Provide ActiveModel errors in an format suitable for API consumers

APIable Model Errors

ActiveModel provides a great framework for handling validations for models. It easily allows you to add any validation message to any attribute however these arbitary strings aren't very helpful if you want to deliver validation errors to APIs. API developers don't want to see Number is too long (maximum is 5 characters), they would much rather see something they can handle programatically like too_long or blank.

This gem extends the ActiveModel::Errors class to allow for a more API-friendly hash of errors to be returned.

Installation

gem "apiable_model_errors"

Usage

Once you've installed the gems, you can call the to_api_hash method on any ActiveModel::Errors object.

user = User.new(params)
unless user.valid?
  user.errors.to_api_hash
end

Example Output

When using this you'll receive a ruby hash however you can easily convert this into JSON by calling to_json on the hash.

{
  "name":[
    {
      "code":"too_long",
      "message":"is too long (maximum is 4 characters)",
      "options":{
        "count":4
      }
    }
  ]
}

As you can see you'll receive the code, the actual translated message from ActiveModel and any options.

has_message?

In addition to provide the to_api_hash method, we also provide a method called has_message? which allows you to determine if a message exists for a given attribute. This is similar to the added? however does not require that you provide all options to see if a message has been added.

# See if there are any :too_long messages on the name attribute
user.errors.has_message?(:name, :too_long)
# See if there are any :too_long messages on the name attribute
# with the options provided.
user.errors.has_message?(:name, :too_long, :count => 4)
# See if there are any :blank messages on the name attribute
user.errors.has_message?(:name, :blank)