koss-lebedev

class Contact < ActiveRecord::Base
  has_dynamic_attributes

  # ... other code
end

koss-lebedev

class ContactAttributeProvider

  def initialize(model)
    @model = model
  end

  def call
    [
      ActiveDynamic::AttributeDefinition.new('age', datatype: ActiveDynamic::DataType::Integer, default_value: 18),
      ActiveDynamic::AttributeDefinition.new('description')

koss-lebedev

class ContactAttributeProvider

  def initialize(model)
    @model = model
  end
  def call
    ContactAttribute.all.map do |attr|
      ActiveDynamic::AttributeDefinition.new(
        attr.name, datatype: attr.datatype,
        required: attr.required?

koss-lebedev

contact = Contact.new

# first_name is a regular attribute mapped to
# a column in contacts table
contact.first_name = 'John'

# age attribute was added dynamically
contact.age = 27

contact.save

koss-lebedev

def dynamic_attribute_inputs(form, model)
  inputs = model.dynamic_attributes.map do |attr|
    options = {
        label: attr.display_name,
        as: datatype_mapping(attr.datatype)
    }
    form.input attr.name, options
  end

  safe_join inputs

koss-lebedev

<%= simple_form_for(contact) do |f| %>
  ... code omitted
  <%= f.input :first_name %>
  <%= f.input :last_name %>
  <%= dynamic_attribute_inputs(f, contact) %>

  <%= f.button :submit %>
<% end %>

koss-lebedev

def contact_params
  params.require(:contact).permit(
    *Contact.new.dynamic_attributes.map(&:name), :first_name)
end

koss-lebedev

config.provider_class = CustomAttributeResolver

koss-lebedev

import React, { FunctionComponent } from 'react'

type Props = {
  posts: readonly RedditPost[]
  subreddit: string
}

const Posts: FunctionComponent<Props> = ({ posts, subreddit }) => (
  <div>
    <h1>Posts in "{subreddit}"</h1>

koss-lebedev

/*
 * ERROR: Property 'getInitialProps' does not exist on type 'FunctionComponent<Props>'.
 */
Posts.getInitialProps = async () => {
  const subreddit = 'typescript'
  const response = await fetch(`https://www.reddit.com/r/${subreddit}.json`)
  const result = await response.json() as RedditResult

  return {
    subreddit,