Extracting hash key that may or may not be an array - ruby-on-rails

Question

I'm making an API call that returns XML (JSON also available) and the response body will show errors if any. There may be only one error or multiple errors. When the XML (or JSON) is parsed into a hash, the key that holds the errors will be an array when multiple errors are present but will be just a standard key when only one error is present. This makes parsing difficult as I can't seem to come up with one line of code that would fit both cases
The call to the API returns this when one error
<?xml version=\"1.0\" encoding=\"utf-8\"?><response><version>1.0</version><code>6</code><message>Data validation failed</message><errors><error><parameter>rptFilterValue1</parameter><message>Parameter is too small</message></error></errors></response>
And this when multiple errors
<?xml version=\"1.0\" encoding=\"utf-8\"?><response><version>1.0</version><code>6</code><message>Data validation failed</message><errors><error><parameter>rptFilterValue1</parameter><message>Parameter is too small</message></error><error><parameter>rptFilterValue2</parameter><message>Missing required parameter</message></error></errors></response>
I use the following to convert the XML to a Hash
Hash.from_xml(response.body).deep_symbolize_keys
This returns the following hash.
When there is only one error, the hash looks like this
{:response=>{:version=>"1.0", :code=>"6", :message=>"Data validation failed", :errors=>{:error=>{:parameter=>"rptFilterValue1", :message=>"Parameter is too small"}}}}
When there are 2 errors, the hash looks like this
{:response=>{:version=>"1.0", :code=>"6", :message=>"Data validation failed", :errors=>{:error=>[{:parameter=>"rptFilterValue1", :message=>"Parameter is too small"}, {:parameter=>"rptFilterValue2", :message=>"Missing required parameter"}]}}}
When I first tested the API response, I had multiple errors so the way I went about getting the error message was like this
data = Hash.from_xml(response.body).deep_symbolize_keys
if data[:response].has_key?(:errors)
errors = data[:response][:errors][:error].map{|x| "#{x.values[0]} #{x.values[1]}"}
However when there is only one error, the code errors out with undefined method 'values' for parameter
The only actual workaround I found was to test the class of the error key. When Array I use one method for extracting and when Hash I use another method.
if data[:response][:errors][:error].class == Array
errors = data[:response][:errors][:error].map{|x| "#{x.values[0]} #{x.values[1]}"}
else
errors = data[:response][:errors][:error].map{|x| "#{x[1]}"}
end
But I just hate hate hate it. There has to be a way to extract xml/json data from a key that may or may not be an array. The solution may be in the conversion from xml to hash rather than when parsing the actual hash. I couldn't find anything online.
I'll appreciate any help or tip.

Answer 1

If you're using Rails, Array#wrap is available if you can do your .dig first:
single = {:response=>{:version=>"1.0", :code=>"6", :message=>"Data validation failed", :errors=>{:error=>{:parameter=>"rptFilterValue1", :message=>"Parameter is too small"}}}}
Array.wrap(single.dig(:response, :errors, :error))
This returns an Array of size 1:
[
{
:message => "Parameter is too small",
:parameter => "rptFilterValue1"
}
]
For multiples:
multiple = {:response=>{:version=>"1.0", :code=>"6", :message=>"Data validation failed", :errors=>{:error=>[{:parameter=>"rptFilterValue1", :message=>"Parameter is too small"}, {:parameter=>"rptFilterValue2", :message=>"Missing required parameter"}]}}}
Array.wrap(multiple.dig(:response, :errors, :error))
This returns an Array of size 2:
[
{
:message => "Parameter is too small",
:parameter => "rptFilterValue1"
},
{
:message => "Missing required parameter",
:parameter => "rptFilterValue2"
}
]

Answer 2

You can parse XML with Nokogiri and xpath, which returns array even if selector points out single element
errors = Nokogiri::XML(xml_response).xpath('//error')
errors.map { |e| e.children.each_with_object({}) { |x, h| h[x.name] = x.content } }
Your API response with single error gives
=> [{"parameter"=>"rptFilterValue1", "message"=>"Parameter is too small"}]
and API result with multiple errors
=> [{"parameter"=>"rptFilterValue1", "message"=>"Parameter is too small"}, {"parameter"=>"rptFilterValue2", "message"=>"Missing required parameter"}]
If there's no error elements you'll get an empty array.