有没有办法将一个块传递给update_attributes？

Question

I'm using Rails 4.2.1. My table has a height column. Is there a way to make a height conversion on the params passed in by the user? Something like:

class WhateverController < ApplicationController
  def update
    current_user.update_attributes(user_params) do |u|
      u.height = convert_height_from_feet_to_inches
    end
  end

  private

    def user_params
      params.require(:user).permit(:name, :height_feet, :height_inches, :weight)
    end

    def convert_height_from_feet_to_inches
      (user_params[:height_feet] * 12) + user_params[:height_inches]
    end

end

For some reason update_attributes is not processing the block I'm trying to pass it. Not sure why you wouldn't be able to pass a block to update_attributes.

Answer 1

You should do this in the model, not the controller. Using virtual attributes you can ensure that setting either height_feet or height_inches will update height with the correct value, and vice versa:

class User < ActiveRecord::Base
  attr_reader :height_feet, :height_inches

  def height_feet=(feet)
    @height_feet = feet.present? ? feet.to_i : feet
    assign_height_from_feet_inches!
  end

  def height_inches=(inches)
    @height_inches = inches.present? ? inches.to_i : inches
    assign_height_from_feet_inches!
  end

  def height=(inches)
    self.height_feet, self.height_inches = inches.divmod(12)
  end

  private
  def assign_height_from_feet_inches!
    self[:height] =
      if self.height_feet.nil? || self.height_inches.nil?
        nil
      else
        self.height_feet * 12 + self.height_inches
      end
  end
end

Now in the controller you can just do this, and the rest will happen automatically:

current_user.update_attributes(user_params)

This will cause the height attribute to be automatically calculated every time the record is saved.