til/rails/remove-blank-values-from-a-hash.md

Remove Blank Values From A Hash

Ruby's Enumerable has a method #compact that will remove nil values from Enumerable objects like hashes and arrays.

> { one: nil, two: 2, three: "" }.compact
=> {two: 2, three: ""}
> [nil, 2, ""].compact
=> [2, ""]

That is often what I want because I'm thinking in terms of values being either nil or valid value.

Sometimes I want to remove all blank values, not just the nil ones. This happens in a Rails context like in a controller when dealing with parameters from a request -- a form field was left blank ("") or no options were picked from the multi-select ([]).

Rails adds #compact_blank to Enumerable to support these cases. Consider that #compact corresponds to #nil? where as #compact_blank corresponds to #blank?.

Here is the example hash pulled from the docs:

> { a: "", b: 1, c: nil, d: [], e: false, f: true }.compact
=> {a: "", b: 1, d: [], e: false, f: true}
> { a: "", b: 1, c: nil, d: [], e: false, f: true }.compact_blank
=> {b: 1, f: true}

I might want to compact_blank a set of search parameters coming from the client before passing it into my search service:

class BooksController < BaseController
  def search
    @results = SearchService.call(search_params.compact_blank)
  end

  private

  def search_params
    params.permit(...)
  end
end