QueryableHash

Find data in Hashes using dot notation queries.

We use QueryableHash to parse Ruby Hashes built from JSON API data. It works especially well when the target data is erratic.

Examples

Data to query

data = {
  glossary: {
    title: "example glossary",
    gloss_div: {
      title: "S",
      gloss_list: {
        gloss_entry: {
          id: "SGML",
          sort_as: "SGML",
          gloss_term: "Standard Generalized Markup Language",
          acronym: "SGML",
          abbrev: "ISO 8879:1986",
          gloss_def: {
            para: "A meta-markup language, used to create markup languages such as DocBook.",
            gloss_see_also: ["GML", "XML"]
          },
          gloss_see: "markup"
        }
      }
    }
  }
}

Find first match

queryable = QueryableHash.wrap(data)
queryable.get("glossary.gloss_div.gloss_list.gloss_entry.id") #=> "SGML"

Find first match using multiple queries

queryable = QueryableHash.wrap(data)
queryable.get("this.key.does.not.exist", "glossary.gloss_div.gloss_list.gloss_entry.id") #=> "SGML"

Find all matches

queryable = QueryableHash.wrap(data)
queryable.get_all(
  "glossary.title",
  "glossary.gloss_div.gloss_list.gloss_entry.gloss_term",
  "glossary.gloss_div.gloss_list.gloss_entry.gloss_def.para"
)
#=> [ "example glossary",
#     "Standard Generalized Markup Language",
#     "A meta-markup language, used to create markup languages such as DocBook." ]

# or assign the results

title, term, para = queryable.get_all(
  "glossary.title",
  "glossary.gloss_div.gloss_list.gloss_entry.gloss_term",
  "glossary.gloss_div.gloss_list.gloss_entry.gloss_def.para"
)
title #=> "example glossary",
term  #=> "Standard Generalized Markup Language"
param #=> "A meta-markup language, used to create markup languages such as DocBook."

Find deeply nested missing key

queryable = QueryableHash.wrap(data)
queryable.get("this.key.does.not.exist") #=> nil

Assign a custom value to represent nil

queryable = QueryableHash.wrap(data)
queryable.get("this.key.does.not.exist", nil_value: "missing") #=> "missing"

Raise an error when not found

queryable = QueryableHash.wrap(data)
queryable.get("this.key.does.not.exist", raise_when_nil: true) #=> raises QueryableHash::NotFoundError

Set query options on the instance

queryable = QueryableHash.wrap(data, nil_value: "missing")
queryable.get("this.key.does.not.exist")      #=> "missing"
queryable.get("neither.does.this.one")        #=> "missing"
queryable.get("nor.this.one", nil_value: nil) #=> nil

queryable = QueryableHash.wrap(data, raise_when_nil: true)
queryable.get("this.key.does.not.exist")             #=> raises QueryableHash::NotFoundError
queryable.get("neither.does.this.one")               #=> raises QueryableHash::NotFoundError
queryable.get("nor.this.one", raise_when_nil: false) #=> nil

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Also check out: https://github.com/joshbuddy/jsonpath