Module: Kithe::Indexer::ObjExtract

Included in:
Kithe::Indexer
Defined in:
app/indexing/kithe/indexer/obj_extract.rb

Overview

A traject indexer macro that provides an indexing macro to extract values from ruby objects (such as ActiveRecord models, although it does not need to be).

You supply a list of method names, which will be called in turn on the source object and previous results. Each result can be a single object or an array of objects. results are always “collected” when there are multiple results.

For instance, if you have something that looks like this:

my_obj.authors = [ Author.new(first: "joe", last: "smith"), Author.new(first: "mary", last: "jones")]

You index as:

to_field, "author_first", obj_extract("authors", "first")

And get ‘[“joe”, “mary”]` indexed. Method chains “short circuit” safely on nil, so if the source object has a nil `authors`, no error will be raised, and you’ll simply have no extracted values as expected.

In addition to method calls, if an extracted object in the chain is a Hash, a path key given can be a hash key.

For instance, if you had an object such that you could access something like:

source_record.authors.collect(&:name_hash).collect { |hash| hash["first"] }

You could have a traject indexing file that might look like:

to_field("author_first"), obj_dig("authors", "name", "first")

If your path lookup does not end in strings, you may have non-string objects in the traject accumulator. Since most writers at the end of the traject chain expect strings, you may want to use subsequent transformation steps to transform those objects into strings with custom logic.

Empty string values (‘“”`) are ignored/removed from output.

FUTURE: Should we extract this to traject itself? Not sure if we’ll end up putting kithe-tied func in here, or how generalizable it is.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.obj_extractor(obj, path) ⇒ Object 



47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
 
# File 'app/indexing/kithe/indexer/obj_extract.rb', line 47

def self.obj_extractor(obj, path)
  first, *rest = *path

  result = if obj.kind_of?(Array)
    first_path_element = path.shift # remove it from path
    obj.flat_map { |item| obj_extractor(item, [first_path_element]) }
  elsif obj.kind_of?(Hash)
    obj[first]
  else
    obj.send(first)
  end

  if result.nil?
    nil
  elsif rest.empty?
    if result.kind_of?(Array)
      result.collect { |v| v == "" ? nil : v  }.compact # remove empty string and nil
    else
      result == "" ? nil : result # turn empty strings to nil
    end
  else
    # recurse
    obj_extractor(result, rest)
  end
end

Instance Method Details

#obj_extract(*path) ⇒ Object 



41
42
43
44
45
 
# File 'app/indexing/kithe/indexer/obj_extract.rb', line 41

def obj_extract(*path)
  proc do |record, accumulator, context|
    accumulator.concat Array.wrap(Kithe::Indexer::ObjExtract.obj_extractor(record, path))
  end
end