Class: RelationToJSON::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/relation_to_json/base.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(relation, schema) ⇒ Base

Returns a new instance of Base.



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# File 'lib/relation_to_json/base.rb', line 10

def initialize(relation, schema)
  @relation = relation
  @schema = schema
end

Instance Attribute Details

#relation ⇒ Object (readonly)

Returns the value of attribute relation.



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# File 'lib/relation_to_json/base.rb', line 8

def relation
  @relation
end

#schema ⇒ Object (readonly)

Returns the value of attribute schema.



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# File 'lib/relation_to_json/base.rb', line 8

def schema
  @schema
end

Instance Method Details

#as_json ⇒ Object 



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# File 'lib/relation_to_json/base.rb', line 15

def as_json
  # put everything here, anything else is private
  attributes, schema_associations = schema
    .partition { |e| e.is_a?(Symbol) }
  schema_associations = schema_associations.first.dup || []

  attributes = Set[:id] + attributes

  reflections = RelationToJSON::ReflectionBuilder.build(schema_associations, relation)
  schema_associations.each do |schema_association, association_attributes|
    reflection = reflections[schema_association]

    case reflection
    when RelationToJSON::BelongsToReflection
      attributes << reflection.foreign_key.to_sym
    when RelationToJSON::HasOneReflection
      association_attributes << reflection.foreign_key.to_sym
    end
  end

  raise_unless_all_attributes_present_on_model!(relation, attributes)

  result = relation
    .reload # if when the relation isn't loaded, it may have strange ordering
    .pluck(*attributes)
    .map { |plucked| attributes.zip(Array.wrap(plucked)).to_h }

  transposed = transpose(result)

  reflections.each do |reflection_name, reflection|
    foreign_key = reflection.foreign_key
    primary_key = reflection.primary_key

    # if the current schema still has associations
    # then we need to recursively find the JSON
    # representation of that association
    # Otherwise, we can perform a shallow .pluck
    # of the association attributes
    # and map them back onto the transposed hash
    # this returns an array of hashes that map association attributes to plucked values
    plucked_values = reflection.pluck_association_columns(transposed)

    case reflection
    when RelationToJSON::BelongsToReflection
    # build a temporary mapping of id => assigned_attributes
      associated_model_primary_key_indexed_plucked_values = plucked_values
          .to_h { |attrs| [attrs&.fetch(primary_key, nil), attrs] }
          .compact

      result.each do |record|
        foreign_key_value = record[foreign_key]
        plucked_values = associated_model_primary_key_indexed_plucked_values[foreign_key_value]
        record[reflection_name] = plucked_values
        record.except!(foreign_key)
      end
    when RelationToJSON::HasOneReflection
    # build a temporary mapping of id => assigned_attributes
      associated_model_foreign_key_indexed_plucked_values = plucked_values
        .to_h { |attrs| [attrs&.fetch(foreign_key, nil), attrs] }
        .compact

      result.each do |record|
        primary_key_value = record[primary_key]
        plucked_values = associated_model_foreign_key_indexed_plucked_values[primary_key_value]
        plucked_values.except!(foreign_key) if plucked_values
        record[reflection_name] = plucked_values
      end
    end
  end

  result&.map { |partial| partial.with_indifferent_access }
end