How to JSON Data (hash) containing arrays in Ruby

Question

I'm trying to find a way to sort JSON data in ruby. It's stored as a fairly complicated (I think so anyway) hash that looks like this:

{
    "allergies": {
        "allergy": [
            {
                "id": "11426793",
                "name": "Milk",
                "category": "Food Allergy",
                "createdPerson": "AGUDELO-HERNANDEZ  ARCADIO",
                "onsetDate": "2014-05-05T00:29:28-04:00"
            }, {
                "id": "11426788",
                "name": "Antibiotics",
                "category": "Drug Allergy",
                "createdPerson": "Smith John H",
                "onsetDate": "2014-05-04T22:29:28-04:00"
            }
        ]
    },
    "responseErrors": {
        "responseError": []
    }
}

There's a lot more "Allergy" objects that exist in the actual data, and I want to be able to sort them by the "onsetDate" then by "name". I've tried:

sorted = @allergies["allergies"].sort_by { |hsh| hsh["name"] }

but I get the following error:

no implicit conversion of String into Integer (TypeError)

Kalman · Accepted Answer · 2014-05-08 02:25:51Z

1

You were almost there:

require "json"

str = <<EOS 
 {
  "allergies": {
    "allergy": [
    {
      "id": "11426793",
      "name": "Milk",
      "category": "Food Allergy",
      "createdPerson": "AGUDELO-HERNANDEZ  ARCADIO",
      "onsetDate": "2014-05-05T00:29:28-04:00"
   },
   {
     "id": "11426788",
     "name": "Antibiotics",
     "category": "Drug Allergy",
     "createdPerson": "Smith John H",
     "onsetDate": "2014-05-04T22:29:28-04:00"
   }

]
},
"responseErrors": {
  "responseError": []
}
}
EOS

@allergies = JSON.parse(str)
puts @allergies["allergies"]["allergy"].sort_by { |hsh| hsh["name"] }

You have JSON (not hash), so you first have to parse it from JSON into hash. Also, the array you are trying to sort is 2 levels deep.

answered May 8, 2014 at 2:25

Kalman

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Comments

Arie Xiao · Accepted Answer · 2014-05-08 02:39:01Z

@allergies["allergies"] returns a hash, which is:

{
    "allergy": [
        {
            "id": "11426793",
            "name": "Milk",
            "category": "Food Allergy",
            "createdPerson": "AGUDELO-HERNANDEZ  ARCADIO",
            "onsetDate": "2014-05-05T00:29:28-04:00"
        }, {
            "id": "11426788",
            "name": "Antibiotics",
            "category": "Drug Allergy",
            "createdPerson": "Smith John H",
            "onsetDate": "2014-05-04T22:29:28-04:00"
        }
    ]
}

Calling sort_by on a hash, it will yield each key-value pairs to the block. So in

@allergies["allergies"].sort_by { |hsh| hsh["name"] }

hsh is an array. Array#[] expects Integer as its argument. It will try to convert "name" to Integer, and fails with the error you seen.

You need

@allergies["allergies"]["allergy"].sort_by { |hsh| hsh["name"] }

or, if you want to sort the values in place, so that the original data will have sorted allergy, use sort_by!

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