Pattern: Missing use of index_by
Issue: -
This rule looks for uses of each_with_object({}) { ... }, map { ... }.to_h, and Hash[map { ... }] that are transforming an enumerable into a hash where the values are the original elements. Rails provides the index_by method for this purpose.
# bad
[1, 2, 3].each_with_object({}) { |el, h| h[foo(el)] = el }
[1, 2, 3].map { |el| [foo(el), el] }.to_h
Hash[[1, 2, 3].collect { |el| [foo(el), el] }]
# good
[1, 2, 3].index_by { |el| foo(el) }