Add render_nil: true to change to_hash result

[martinnicolas]

Hi!. I notice that calling to_hash method on a Shale::Mapper object, nil values are not rendered. I can change this using https://www.shalerb.org/#rendering-nil-values render_nil: true but only for shale methods to_json, to_csv etc. It could be a nice approach to implement something similar for to_hash. Thanks for your job!

[kgiszczak]

hey, you can absolutely do this:

require 'shale'

class Person < Shale::Mapper
  attribute :first_name, Shale::Type::String
  attribute :last_name, Shale::Type::String
  attribute :age, Shale::Type::Integer

  hsh do
    map 'first_name', to: :first_name, render_nil: true
    map 'last_name', to: :last_name, render_nil: false
    map 'age', to: :age, render_nil: true
  end
end

puts Person.new(
  first_name: nil,
  last_name: nil,
  age: nil
).to_hash(pretty: true)

# => {"first_name"=>nil, "age"=>nil}

[martinnicolas]

Hi. thats nice! but is not the my case. I would try to explain a lit better.

  require 'shale'

  class Person < Shale::Mapper
    attribute :first_name, Shale::Type::String
    attribute :last_name, Shale::Type::String
    attribute :age, Shale::Type::Integer

    csv do
      map 'first_name', to: :first_name, render_nil: true
      map 'last_name', to: :last_name, render_nil: false
      map 'age', to: :age, render_nil: true
    end
  end

  puts Person.new(
    first_name: nil,
    last_name: nil,
    age: nil
  ).to_hash

# => {}

I need the csv block because I'm importing a csv file. And I need to_hash for using https://github.com/zdennis/activerecord-import to import content into my database. Could be possible to define another block for hsh? like this?

  require 'shale'

  class Person < Shale::Mapper
    attribute :first_name, Shale::Type::String
    attribute :last_name, Shale::Type::String
    attribute :age, Shale::Type::Integer

    csv do
      map 'first_name', to: :first_name, render_nil: true
      map 'last_name', to: :last_name, render_nil: false
      map 'age', to: :age, render_nil: true
    end

    hsh do
      map 'first_name', to: :first_name, render_nil: true
      map 'last_name', to: :last_name, render_nil: false
      map 'age', to: :age, render_nil: true
    end
  end

[kgiszczak]

yes, you can define as many blocks as you want, this is valid:

  require 'shale'

  class Person < Shale::Mapper
    attribute :first_name, Shale::Type::String
    attribute :last_name, Shale::Type::String
    attribute :age, Shale::Type::Integer

    csv do
      map 'first_name', to: :first_name, render_nil: true
      map 'last_name', to: :last_name, render_nil: false
      map 'age', to: :age, render_nil: true
    end

    hsh do
      map 'first_name', to: :first_name, render_nil: true
      map 'last_name', to: :last_name, render_nil: false
      map 'age', to: :age, render_nil: true
    end
    
    json do
      ...
    end

    toml do
      ...
    end

    xml do
      ...
    end
  end

[martinnicolas]

Nice! I was using this little hack. To prevent defining all maps again. But I think is better to redefine the mapping block for each format. Isnt it?

def to_hash
  instance_variables.each_with_object({}) do |instance_variable_name, hash|
    hash[instance_variable_name.to_s.delete("@")] = instance_variable_get(instance_variable_name)
  end
end