Class: JsonDataExtractor::Extractor

Inherits:
Object
  • Object
show all
Defined in:
lib/json_data_extractor/extractor.rb

Overview

does the main job of the gem

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(json_data, modifiers = {}) ⇒ Extractor

Returns a new instance of Extractor.

Parameters:

  • json_data (Hash, String)
  • modifiers (Hash) (defaults to: {}) 


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# File 'lib/json_data_extractor/extractor.rb', line 10

def initialize(json_data, modifiers = {})
  @data = json_data.is_a?(Hash) ? Oj.dump(json_data, mode: :compat) : json_data
  @modifiers = modifiers.transform_keys(&:to_sym)
  @results = {}
  @path_cache = {}
end

Instance Attribute Details

#data ⇒ Object (readonly)

Returns the value of attribute data.



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# File 'lib/json_data_extractor/extractor.rb', line 6

def data
  @data
end

#modifiers ⇒ Object (readonly)

Returns the value of attribute modifiers.



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# File 'lib/json_data_extractor/extractor.rb', line 6

def modifiers
  @modifiers
end

#schema_cache ⇒ Object (readonly)

Returns the value of attribute schema_cache.



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# File 'lib/json_data_extractor/extractor.rb', line 6

def schema_cache
  @schema_cache
end

Class Method Details

.with_schema(schema, modifiers = {}) ⇒ Extractor

Creates a new extractor with a pre-processed schema

Parameters:

  • schema (Hash) —

    schema of the expected data mapping

  • modifiers (Hash) (defaults to: {}) —

    modifiers to apply to the extracted data

Returns:

  • (Extractor) —

    an extractor initialized with the schema



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# File 'lib/json_data_extractor/extractor.rb', line 21

def self.with_schema(schema, modifiers = {})
  extractor = new({}, modifiers)
  extractor.instance_variable_set(:@schema_cache, SchemaCache.new(schema))
  extractor
end

Instance Method Details

#add_modifier(modifier_name, callable = nil, &block) ⇒ Object

Parameters:

  • modifier_name (String, Symbol)
  • callable (#call, nil) (defaults to: nil) —

    Optional callable object

Raises:

  • (ArgumentError) 


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# File 'lib/json_data_extractor/extractor.rb', line 48

def add_modifier(modifier_name, callable = nil, &block)
  modifier_name = modifier_name.to_sym unless modifier_name.is_a?(Symbol)
  modifiers[modifier_name] = callable || block

  return if modifiers[modifier_name].respond_to?(:call)

  raise ArgumentError, 'Modifier must be a callable object or a block'
end

#extract(schema) ⇒ Object

Parameters:

  • schema (Hash) —

    schema of the expected data mapping



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# File 'lib/json_data_extractor/extractor.rb', line 58

def extract(schema)
  schema.each do |key, val|
    element = JsonDataExtractor::SchemaElement.new(val.is_a?(Hash) ? val : { path: val })

    path = element.path
    json_path = path ? (@path_cache[path] ||= JsonPath.new(path)) : nil

    extracted_data = json_path&.on(@data)

    if extracted_data.nil? || extracted_data.empty?
      # we either got nothing or the `path` was initially nil
      @results[key] = element.fetch_default_value
      next
    end

    # check for nils and apply defaults if applicable
    extracted_data.map! { |item| item.nil? ? element.fetch_default_value : item }

    # apply modifiers if present
    extracted_data = apply_modifiers(extracted_data, element.modifiers) if element.modifiers.any?

    # apply maps if present
    @results[key] = element.maps.any? ? apply_maps(extracted_data, element.maps) : extracted_data

    @results[key] = resolve_result_structure(@results[key], element)
  end

  @results
end

#extract_from(json_data) ⇒ Hash

Extracts data from the provided json_data using the cached schema

Parameters:

  • json_data (Hash, String) —

    the data to extract from

Returns:

  • (Hash) —

    the extracted data

Raises:

  • (ArgumentError) 


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# File 'lib/json_data_extractor/extractor.rb', line 30

def extract_from(json_data)
  # Ensure we have a schema cache
  raise ArgumentError, 'No schema cache available. Use Extractor.with_schema first.' unless @schema_cache

  # Reset results
  @results = {}

  # Update data
  @data = json_data.is_a?(Hash) ? Oj.dump(json_data, mode: :compat) : json_data

  # Extract data using cached schema
  extract_using_cache

  @results
end