Ejemplo Simple de uso de DataMapper: Agenda

DataMapper.setup

[~/sinatra/sinatra-datamapper/data_mapper_example_agenda(master)]$ cat app.rb
#!/usr/bin/env ruby
require 'rubygems'
require 'sinatra'
require 'haml'
require 'data_mapper'

# full path!
DataMapper.setup( :default, "sqlite3://#{Dir.pwd}/agenda.db" )

We must specify our database connection.

We need to make sure to do this before you use our models, i.e. before we actually start accessing the database.

Modelos

# Define the model
class Contact
  include DataMapper::Resource

  property :id, Serial
  property :firstname, String
  property :lastname, String
  property :email, String
end

The Contact model is going to need to be persistent, so we'll include DataMapper::Resource.

The convention with model names is to use the singular, not plural version.

Module: DataMapper::Resource

+ (Object) included(model) private
Makes sure a class gets all the methods when it includes Resource.

Inside your class, call the property method for each property you want to add. The only two required arguments are the name and type, everything else is optional.

Primary keys are not automatically created for you. You MUST configure at least one key property on your data-store.

More often than not, you'll want an auto-incrementing integer as a primary key, so DM has a shortcut:

   property :id, Serial

(Property) property(name, type, options = {})
Defines a Property on the Resource

See the section Properties in datamapper.org.

DataMapper.auto_upgrade!

  1. This tries to make the schema match the model.
  2. It will CREATE new tables, and add columns to existing tables.
  3. It won't change any existing columns though (say, to add a NOT NULL constraint) and it doesn't drop any columns.
  4. Both these commands also can be used on an individual model (e.g. Song.auto_migrate!)

Rutas

# Show list of contacts
%w{/ /contacts/?}.each do |r|
  get r do
    haml :list, :locals => { :cs => Contact.all }
  end
end

# Show form to create new contact
get '/contacts/new' do
  haml :form, :locals => {
    :c => Contact.new,
    :action => '/contacts/create'
  }
end

# Create new contact
post '/contacts/create' do
  c = Contact.new
  c.attributes = params
  c.save

  redirect("/contacts/#{c.id}")
end

# Show form to edit contact
get '/contacts/:id/edit' do|id|
  c = Contact.get(id)
  haml :form, :locals => {
    :c => c,
    :action => "/contacts/#{c.id}/update"
  }
end

# Show form to find a contact by firstname
get '/contacts/findform' do
  haml :findform, :locals => {
    :action => "/contacts/find"
  }
end

post '/contacts/find' do
  puts "params = #{params}"
  s = params.select { |k,v| v != '' }
  #s[:order] = [ :lastname.desc]
  s[:order] = [ :lastname.asc]
  puts "selected #{s}"
  cs = Contact.all(s)
  puts cs
  haml :list, :locals => { :cs => cs }
end
#
# Edit a contact
post '/contacts/:id/update' do|id|
  puts "en /contacts/:id/update: params = #{params} id = #{id}"
  c = Contact.get(id)
  puts c.inspect
  
  puts "Fail while recording #{c}" unless c.update(
      :firstname => params[:firstname], 
      :lastname  => params[:lastname], 
      :email     => params[:email])

  redirect "/contacts/#{id}"
end

# Delete a contact
post '/contacts/:id/destroy' do|id|
  c = Contact.get(id)
  c.destroy

  redirect "/contacts/"
end

# View a contact
# TODO: Put at bottom?
get '/contacts/:id' do|id|
  c = Contact.get(id)
  haml :show, :locals => { :c => c }
end

__END__

Vistas

__END__
@@ layout
%html
  %head
    %title Agenda
  %body
    = yield
    %a(href="/contacts/") Contact List
    %a(href="/contacts/findform") Find Contact

@@form
%h1 Create a new contact
%form(action="#{action}" method="POST")
  %label(for="firstname") First Name
  %input(type="text" name="firstname" value="#{c.firstname}")
  %br

  %label(for="lastname") Last Name
  %input(type="text" name="lastname" value="#{c.lastname}")
  %br

  %label(for="email") Email
  %input(type="text" name="email" value="#{c.email}")
  %br

  %input(type="submit")
  %input(type="reset")
  %br

- unless c.id == 0
  %form(action="/contacts/#{c.id}/destroy" method="POST")
    %input(type="submit" value="Destroy")
  
@@show
%table
  %tr
    %td First Name
    %td= c.firstname
  %tr
    %td Last Name
    %td= c.lastname
  %tr
    %td Email
    %td= c.email
%a(href="/contacts/#{c.id}/edit") Edit Contact

@@list
%h1 Contacts
%a(href="/contacts/new") New Contact
%table
  - cs.each do|c|
    %tr
      %td= c.firstname
      %td= c.lastname
      %td= c.email
      %td
        %a(href="/contacts/#{c.id}") Show
      %td
        %a(href="/contacts/#{c.id}/edit") Edit

@@findform
%h1 Find a contact for firstname
%form(action="#{action}" method="POST")
  %label(for="firstname") First Name
  %input(type="text" name="firstname" value="")
  %br

  %label(for="lastname") Last Name
  %input(type="text" name="lastname" value="")
  %br

  %label(for="email") Email
  %input(type="text" name="email" value="")
  %br

  %input(type="submit")
  %input(type="reset")
  %br

Enlaces

  1. Documentación del módulo DataMapper en RubyDoc
  2. https://github.com/crguezl/datamapper_example
  3. https://github.com/crguezl/datamapper-intro



Subsecciones
Casiano Rodriguez León 2015-06-18