Class: YamlExporter::Importer

Inherits:
Object
  • Object
show all
Defined in:
lib/yaml_exporter/importer.rb

Overview

Drives the import of a YAML document into a tree of ActiveRecord records.

Works in a single transaction on the root record's class. For every record it touches (root + any owned child) it runs two phases:

1. pre_save  — nodes that mutate columns on *this* record
             (Attribute, OneReference).
2. save!     — the record is now persisted and has an id.
3. post_save — nodes that need parent.id to do their work
             (OneOwned, ManyPositional, ManyFindBy,
              ManyReference, ManyThrough).

Each node is responsible for its own persistence; this class just orchestrates phases and validates unknown keys.

Instance Method Summary collapse

Constructor Details

#initialize(record, structure) ⇒ Importer

Returns a new instance of Importer.



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# File 'lib/yaml_exporter/importer.rb', line 19

def initialize(record, structure)
  @root_record = record
  @root_structure = structure
end

Instance Method Details

#apply(record, structure, data, path:, extra_keys: []) ⇒ Object

Called recursively by nodes that own child records (OneOwned, ManyBase flavors) once they've built or found the child row.

extra_keys lets the caller (typically a many node) declare keys that belong to it, not to structure. Example: find_by: :slug means slug: is legal at the entry level but isn't a declared Attribute on the child — it's the discriminator the parent node consumes. The child's own Attribute setters never see it because no Attribute node declares it; it simply passes validation.



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# File 'lib/yaml_exporter/importer.rb', line 41

def apply(record, structure, data, path:, extra_keys: [])
  data = {} if data.nil?
  unless data.is_a?(Hash)
    raise UnknownAttributeError, "#{describe_path(path)}: expected a mapping, got #{data.class}"
  end

  validate_keys!(structure, data, path: path, extra_keys: extra_keys)

  pre, post = structure.nodes.partition { |n| n.phase == :pre_save }
  pre.each { |n| n.import(record, data, path: path, importer: self) }
  record.save!
  post.each { |n| n.import(record, data, path: path, importer: self) }
end

#import(yaml_string) ⇒ Object 



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# File 'lib/yaml_exporter/importer.rb', line 24

def import(yaml_string)
  @root_record.class.transaction do
    data = parse(yaml_string)
    apply(@root_record, @root_structure, data, path: '')
  end
  @root_record
end