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I'm working with a third-party API. I'm trying to parse JSON using Ruby. JSON response:

{
  "metric_data": {
    "from": "2014-09-22T23:33:20+00:00",
    "to": "2014-09-23T00:03:20+00:00",
    "metrics": [
      {
        "name": "HttpDispatcher",
        "timeslices": [
          {
            "from": "2014-09-22T23:32:00+00:00",
            "to": "2014-09-23T00:01:59+00:00",
            "values": {
              "requests_per_minute": 85700
            }
          }
        ]
      }
    ]
  }
}

The data that I need to access is requests_per_minute. Since JSON.parse returns a Hash, it seems like I would just able to access this using keys:

hash = JSON.parse(response.body)

data = hash["metric_data"]

The previous code would produce a nested level down, like this:

{
  "from": "2014-09-22T23:33:20+00:00",
  "to": "2014-09-23T00:03:20+00:00",
  "metrics": [
    {
      "name": "HttpDispatcher",
      "timeslices": [
        {
          "from": "2014-09-22T23:32:00+00:00",
          "to": "2014-09-23T00:01:59+00:00",
          "values": {
            "requests_per_minute": 85700
          }
        }
      ]
    }
  ]
}

However, if I try to nest any further, the response becomes an Array and I receive an error:

data = hash["metric_data"]["metrics"]["timeslices"]

no implicit conversion of String into Integer (TypeError)

I believe the error is that "metrics" and "timeslices" appear to be JSON Arrays, using [] instead of {}. I really need a sanity check. What am I missing here? I'm just trying to access requests_per_minute.

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  • hash["metric_data"]["metrics"][0]["timeslices"] Commented Sep 23, 2014 at 18:40

1 Answer 1

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6

You're correct, it's parsing "metrics" and "timeslices" each as an Array of Hashes, so try this:

requests_per_minute = hash["metric_data"]["metrics"][0]["timeslices"][0]["values"]["requests_per_minute"]
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2 Comments

Thanks for your answer, I was able to access RPM. I'm curious about how it works: using [0] just allows you access the first element of each nested Array?
Yes, correct. Arrays are index based with the first being 0. Presumably, you could have more than one "metrics" or "timeslices" in the result.