How can I silence or prevent a "Missing hash key" error?

Question

I am getting a JSON response from an API, that I parse with JSON.parse(). I have a loop in my code that on each iteration checks if a certain parameter in the JSON response is equal to a defined string. This is a simpler version of the JSON response I am receiving:

{
  "response": [
    {
      "data": {
        "parameter": "value"
      }
    },
    {
      "data": {
        "parameter": "value2"
      }
    },
    {
      "data": {
        "parameter2": "value"
      }
    }
  ]
}

As you can see only response[0] and response[1] contain parameter. response[2] has parameter2. So if I loop through it with:

while i < responses.size
  response = responses[i]
  if(response.data.parameter == "value")
    *do something*
  end
end

I am gonna get Unhandled exception: Missing hash key: "parameter" when I get to the third iteration. Can I ignore or better, prevent the error from happening?

Answer 1

If you're correctly reading the data as an array of hashes of hashes, you can use has_key? to filter out invalid responses. The following sample code works for me:

responses = {
  "response" => [
    {
      "data" => {
        "parameter" => "value",
      },
    },
    {
      "data" => {
        "parameter" => "value2",
      },
    },
    {
      "data" => {
        "parameter2" => "value",
      },
    },
  ],
}

pp responses

responses["response"].each do |response|
  if response["data"].has_key?("parameter")
    pp response
    valid_response = response["data"]
    if valid_response["parameter"] == "value"
      puts "Doing something..."
    end
  end
end

and produces the following output:

{"response" =>
  [{"data" => {"parameter" => "value"}},
   {"data" => {"parameter" => "value2"}},
   {"data" => {"parameter2" => "value"}}]}
{"data" => {"parameter" => "value"}}
Doing something...
{"data" => {"parameter" => "value2"}}