jcasimir

Transactions

As your business logic gets complex you may need to implement transactions. The classic example is a bank funds transfer from account A to account B. If the withdrawal from account A fails then the deposit to account B should either never take place or be rolled back.

Basics

All the complexity is handled by ActiveRecord::Transactions. Any model class or instance has a method named .transaction. When called and passed a block, that block will be executed inside a database transaction. If there's an exception raised, the transaction will automatically be rolled back.

Example

felipeelias

#!/bin/bash

APP_PATH=/home/applicake/app

# Production environment
export RAILS_ENV="production"

export PATH="/opt/ruby/bin:$PATH"

exit_with_error() {

Randommood

postgres=# \dx
                 List of installed extensions
  Name   | Version |   Schema   |         Description          
---------+---------+------------+------------------------------
 plpgsql | 1.0     | pg_catalog | PL/pgSQL procedural language
(1 row)

postgres=# \dx+
      Objects in extension "plpgsql"
            Object Description             

them0nk

#Model 

@user.should have(1).error_on(:username) # Checks whether there is an error in username 
@user.errors[:username].should include("can't be blank")  # check for the error message 

#Rendering
response.should render_template(:index)

#Redirecting 
response.should redirect_to(movies_path)

mdespuits

#!/bin/bash

main() {
  if [[ $(has_lvh_me) == 1 ]]; then
    echo 'lvh.me is already specified in your hosts file'
  else
    add_lvh_me
    echo 'lvh.me was added to your hosts file!'
  fi
  flush_dns_cache

bbugh

//Get a reference to the alert using the following:

alert = page.driver.browser.switch_to.alert

// and then hit OK with

page.driver.browser.switch_to.alert.accept

// or dismiss it with

hSATAC

package main

import (
    "log"
    "net/http"
)

func redirect(w http.ResponseWriter, r *http.Request) {

    http.Redirect(w, r, "http://www.google.com", 301)

adamwiggins

Make it real

Ideas are cheap. Make a prototype, sketch a CLI session, draw a wireframe. Discuss around concrete examples, not hand-waving abstractions. Don't say you did something, provide a URL that proves it.

Ship it

Nothing is real until it's being used by a real user. This doesn't mean you make a prototype in the morning and blog about it in the evening. It means you find one person you believe your product will help and try to get them to use it.

Do it with style

blaix

On Tue, Mar 12, 2013 at 1:26 PM, Martin Fowler martinfowlercom@gmail.com wrote:

The term pops up in some different places, so it's hard to know what it means without some context. In PoEAA I use the pattern Service Layer to represent a domain-oriented layer of behaviors that provide an API for the domain layer. This may or may not sit on top of a Domain Model. In DDD Eric Evans uses the term Service Object to refer to objects that represent processes (as opposed to Entities and Values). DDD Service Objects are often useful to factor out behavior that would otherwise bloat Entities, it's also a useful step to patterns like Strategy and Command.

It sounds like the DDD sense is the sense I'm encountering most often. I really need to read that book.

The conceptual problem I run into in a lot of codebases is that rather than representing a process, the "service objects" represent "a thing that does the process". Which sounds like a nitpicky difference, but it seems to have a real impact on how people us

rpmuller

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