Refactoring in Practice - Sunnyconf 2010

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:blogs_at => 'alexjsharp.com'
:ships_at => 'github.com/ajsharp' }

IT’S NOT ALL GREEN FIELDS
AND “SOFT LAUNCHES”

large apps are a completely different
beast than small apps

tight code coupling across
domain concepts

these apps become harder to maintain
as size increases

tight domain coupling exposes itself as a
symptom of application size

this talk is about
working with large apps

it’s about staying on the
straight and narrow

process

habit

it’s about ﬁxing bad code.

it’s about responsibly ﬁxing bad code.

it’s about responsibly ﬁxing bad and
improving code.

we’re out of our element without tests

red, green, refactor doesn’t work
without the red

AVOID THE EPIC REFACTOR
(IF POSSIBLE)

what do we mean when
we use the term “refactor”

TRADITIONAL DEFINITION

To refactor code is to change it’s implementation while
maintaining it’s behavior.

- via Martin Fowler, Kent Beck et. al

in web apps this means that the behavior
for the end user remains unchanged

COMMON PROBLEMS
(I.E. ANTI-PATTERNS)

LACK OF TECHNICAL
LEADERSHIP
• Many common anti-pattens violated consistently

• DRY

• single responsibility

• large procedural code blocks

LACK OF PLATFORM
KNOWLEDGE
• Often developers re-engineer features provided by the platform

• frequent offense, but very low-hanging fruit to ﬁx

LACK OF TESTS

A few typical scenarios:

• Aggressive deadlines: “there’s no time for tests”
• Lack of testing experience leads to abandonment of tests
• two ﬁles with tests in a 150+ model app
• “We’ll add tests later”

POOR DOMAIN MODELING

• UDD: UI-driven development

• Unfamiliarity with domain modeling

• probably b/c many apps don’t need it

WRANGLING VIEW LOGIC
WITH A PRESENTER

COMMON PROBLEMS

• i-var bloat

• results in difﬁcult to test controllers

• high barriers like this typically lead to developers just not
testing

• results in brittle views

• instance variables are an implementation, not an interface

THE BILLINGS SCREEN

• Core functionality was simply broken, not working

• This area of the app is somewhat of a “shanty town”

class BillingsController < ApplicationController
def index
@visit_statuses = Visit::Statuses
@visit_status = 'Complete'
@visit_status = params[:visit_status] unless params[:visit_status].blank?

@billing_status =
if @visit_status.upcase != 'COMPLETE' then ''
elsif ( params[:billing_status] && params[:billing_status] != '-' ) then params[:billing_status]
else Visit::Billing_pending
end

@noted = 'true'
@noted = 'false' if params[:noted] == 'false'

@clinics = current_user.allclinics( @practice.id )
@visits = current_clinic.visits.billable_visits(@billing_status, @visit_status).order_by("visit_date")

session[:billing_visits] = @visits.collect{ |v| v.id }
end
end

var! ivar!
i @
ly@ oly
Ho
def index H
ivar!

oly @ r!

H

i va
@billing_status =

!

r @

a

r!

iv ly
end

va
@
@noted = 'true'
o
H

i

@
y
l H

o

oly @

ly
H

o
ivar!
end

H
end

%th=collection_select(:search, :clinic_id, @clinics, :id, :name , {:prompt => "All"},
:class => 'filterable')
%th=select_tag('search[visit_status_eq]',
options_for_select( Visit::Statuses.collect(&:capitalize), @visit_status ), {:class => 'filterable'})
%th=select_tag('search[billing_status_eq]',
options_for_select([ "Pending", "Rejected", "Processed" ], @billing_status), {:class => 'filterable'})
%th=collection_select(:search, :resource_id, @providers, :id, :full_name, { :prompt => 'All' },
%tbody
= render :partial => 'visit', :collection => @visits

SMELLS

• Tricky presentation logic quickly becomes brittle

• Lot’s of hard-to-test, important code

• Needlessly storing constants in ivars

• Craziness going on with @billing_status. Seems important.

def index

@billing_status =
end

@noted = 'true' seems important...maybe for searching?


end
end

def index

@billing_status =
end

@noted = 'true'
@noted = 'false' if params[:noted] == 'false' WTF!?!?

end
end

A QUICK NOTE ABOUT
“PERPETUAL WTF SYNDROME”

TOO MANY WTF’S WILL DRIVE
YOU NUTS

YOU FORGET THAT GOOD
CODE EXISTS

THAT’S ONE REASON WHY
THE NEXT STEP IS SO
IMPORTANT

IT’S KEEPS THE DIALOGUE
POSITIVE

ENGINEERING GOALS

• Program to an interface, not an implementation

• Only one instance variable

• Use extract class to wrap up presentation logic

describe BillingsPresenter do
before do
@practice = mock_model(Practice)
@user = mock_model(User, :practice => @practice) visit = mock_model Visit
@presenter = BillingsPresenter.new({}, @user, @practice) @presenter.stub!(:visits).and_return([visit])
end visit.should_receive(:resource)

describe '#visits' do @presenter.providers
it 'should receive billable_visits' do end
@practice.should_receive(:billable_visits) end
@presenter.visits
end describe '.default_visit_status' do
end it 'is the capitalized version of COMPLETE' do
BillingsPresenter.default_visit_status.should ==
describe '#visit_status' do 'Complete'
it 'should default to the complete status' do end
@presenter.visit_status.should == "Complete" end
end
end describe '.default_billing_status' do
it 'is the capitalized version of COMPLETE' do
describe '#billing_status' do BillingsPresenter.default_billing_status.should ==
it 'should default to default_billing_status' do 'Pending'
@presenter.billing_status.should == end
BillingsPresenter.default_billing_status end
end
describe '#visit_statuses' do
it 'should use the params[:billing_status] if it exists' it 'is the capitalized version of the visit statuses' do
do @presenter.visit_statuses.should == [['All', '']] +
presenter = BillingsPresenter.new({:billing_status => Visit::Statuses.collect(&:capitalize)
'use me'}, @user, @practice) end
presenter.billing_status.should == 'use me' end
end
end describe '#billing_stauses' do
it 'is the capitalized version of the billing statuses' do
describe '#clinics' do @presenter.billing_statuses.should == [['All', '']] +
it 'should receive user.allclinics' do Visit::Billing_statuses.collect(&:capitalize)
@user.should_receive(:allclinics).with(@practice.id) end
@presenter.clinics end
end
end end

describe '#providers' do
it 'should get the providers from the visit' do

class BillingsPresenter
attr_reader :params, :user, :practice
def initialize(params, user, practice)
@params = params
@user = user
@practice = practice
end

def self.default_visit_status
Visit::COMPLETE.capitalize
end

def self.default_billing_status
Visit::Billing_pending.capitalize
end

def visits
@visits ||= practice.billable_visits(params[:search])
end

def visit_status
params[:visit_status] || self.class.default_visit_status
end

def billing_status
params[:billing_status] || self.class.default_billing_status
end

def clinics
@clinics ||= user.allclinics practice.id
end

def providers
@providers ||= visits.collect(&:resource).uniq
end

def visit_statuses
[['All', '']] + Visit::Statuses.collect(&:capitalize)
end

def billing_statuses
[['All', '']] + Visit::Billing_statuses.collect(&:capitalize)
end
end

def index
@presenter = BillingsPresenter.new params, current_user, current_practice

session[:billing_visits] = @presenter.visits.collect{ |v| v.id }
end
end

%th=collection_select(:search, :clinic_id, @presenter.clinics, :id, :name , {:prompt => "All"},
%th=select_tag('search[visit_status_eq]',
options_for_select( Visit::Statuses.collect(&:capitalize), @presenter.visit_status ), {
:class => 'filterable'})
%th=select_tag('search[billing_status_eq]',
options_for_select([ "Pending", "Rejected", "Processed" ], @presenter.billing_status), {:class =>
'filterable'})
%th=collection_select(:search, :resource_id, @presenter.providers, :id, :full_name, { :prompt => 'All' },
%tbody
= render :partial => 'visit', :collection => @presenter.visits

WINS

• Much cleaner, more testable controller

• Much less brittle view template

• The behavior of this action actually works

UPDATE ACTION CRAZINESS

• Update a collection of associated objects in the parent object’s
update action

Object Model
Medical History

*
join model
*

Existing Condition

def update
@medical_history = @patient.medical_histories.find(params[:id])

@medical_history.taken_date = Date.today if @medical_history.taken_date.nil?

success = true
conditions = @medical_history.existing_conditions_medical_histories.find(:all)
params[:conditions].each_pair do |key,value|
condition_id = key.to_s[10..-1].to_i
condition = conditions.detect {|x| x.existing_condition_id == condition_id }
if condition.nil?
success = @medical_history.existing_conditions_medical_histories.create(
:existing_condition_id => condition_id, :has_condition => value) && success
elsif condition.has_condition != value
success = condition.update_attribute(:has_condition, value) && success
end
end
respond_to do |format|
if @medical_history.update_attributes(params[:medical_history]) && success
format.html {
flash[:notice] = 'Medical History was successfully updated.'
redirect_to( patient_medical_histories_url(@patient) ) }
format.xml { head :ok }
format.js
else
format.html { render :action => "edit" }
format.xml { render :xml => @medical_history.errors, :status => :unprocessable_entity }
format.js { render :text => "Error Updating History", :status => :unprocessable_entity}
end
end
end

def update


success = true
if condition.nil?
elsif condition.has_condition != value smell-fest
end
end
format.html {
format.js
else
end
end
end

Lot’s of violations:

1. Fat model, skinny controller

2. Single responsibility

3. Not modular

4. Repetition of rails

5. Really hard to ﬁt on a slide

Let’s focus here


if condition.nil?
end
end

STEP 3: IDENTIFY
ENGINEERING GOALS

I want to refactor in the following ways:

1. Push this code into the model

2. Extract varying logic into separate methods

We need to write some characterization tests and
get this action under test so we can ﬁgure out
what it’s doing.

This way we can rely on an automated testing
workﬂow for instant feedback

describe MedicalHistoriesController, "PUT update" do
context "successful" do
before :each do
@user = Factory(:practice_admin)
@patient = Factory(:patient_with_medical_histories, :practice => @user.practice)
@medical_history = @patient.medical_histories.first

@condition1 = Factory(:existing_condition)
@condition2 = Factory(:existing_condition)

stub_request_before_filters @user, :practice => true, :clinic => true

params = { :conditions =>
{ "condition_#{@condition1.id}" => "true",
"condition_#{@condition2.id}" => "true" },
:id => @medical_history.id,
:patient_id => @patient.id
}

put :update, params
end

it { should redirect_to patient_medical_histories_url }
it { should_not render_template :edit }

it "should successfully save a collection of conditions" do
@medical_history.existing_conditions.should include @condition1
@medical_history.existing_conditions.should include @condition2
end
end
end

we can eliminate this, b/c it’s an association of this
model


if condition.nil?
end
end

Next, do extract method on this line
condition = existing_conditions_medical_histories.detect {|x| x.existing_condition_id ==
condition_id }
if condition.nil?
success = existing_conditions_medical_histories.create(
end
end

Cover this new method w/ tests
condition_id = get_id_from_string(key)
condition_id }
if condition.nil?
end
end

???
condition_id }
if condition.nil?
end
end

i.e. ecmh.ﬁnd(:ﬁrst, :conditions => { :existing_condition_id => condition_id })
condition_id }
if condition.nil?
end
end

do extract method here...
condition_id }
if condition.nil?
end
end

???
condition = find_existing_condition(condition_id)
if condition.nil?
end
end

i.e. create or update
condition = find_existing_condition(condition_id)
if condition.nil?
end
end

describe MedicalHistory, "#update_conditions" do
context "when passed a condition that is not an existing conditions" do
before do
@medical_history = Factory(:medical_history)
@condition = Factory(:existing_condition)

@medical_history.update_conditions({ "condition_#{@condition.id}" => "true" })
end

it "should add the condition to the existing_condtions association" do
@medical_history.existing_conditions.should include @condition
end

it "should set the :has_condition attribute to the value that was passed in" do
@medical_history.existing_conditions_medical_histories.first.has_condition.should == true
end
end

context "when passed a condition that is an existing condition" do
before do
ecmh = Factory(:existing_conditions_medical_history, :has_condition => true)
@medical_history = ecmh.medical_history
@condition = ecmh.existing_condition

@medical_history.update_conditions({ "condition_#{@condition.id}" => "false" })
end

it "should update the existing_condition_medical_history record" do
@medical_history.existing_conditions.should_not include @condition
end

it "should set the :has_condition attribute to the value that was passed in" do
@medical_history.existing_conditions_medical_histories.first.has_condition.should == false
end
end

end

def update_conditions(conditions_param = {})
conditions_param.each_pair do |key, value|
create_or_update_condition(get_id_from_string(key), value)
end if conditions_param
end

private
def create_or_update_condition(condition_id, value)
condition = existing_conditions_medical_histories.find_by_existing_condition_id(condition_id)
condition.nil? ? create_condition(condition_id, value) : update_condition(condition, value)
end

def create_condition(condition_id, value)
existing_conditions_medical_histories.create(
:existing_condition_id => condition_id,
:has_condition => value
)
end

def update_condition(condition, value)
condition.update_attribute(:has_condition, value) unless condition.has_condition == value
end

We went from this mess in the controller
def update


success = true
if condition.nil?
end
end
format.html {
format.js
else
end
end
end

To this in the controller...

def update

if( @medical_history.update_attributes(params[:medical_history]) &&
@medical_history.update_conditions(params[:conditions]) )
format.html {
format.js
else
format.js { render :text => "Error Updating History",
:status => :unprocessable_entity }
end
end
end

and this in the model

def update_conditions(conditions_param = {})
conditions_param.each_pair do |key, value|
create_or_update_condition(get_id_from_string(key), value)
end if conditions_param
end

private
def create_or_update_condition(condition_id, value)
condition = existing_conditions_medical_histories.find_by_existing_condition_id(condition_id)
condition.nil? ? create_condition(condition_id, value) : update_condition(condition, value)
end

def create_condition(condition_id, value)
existing_conditions_medical_histories.create(
:existing_condition_id => condition_id,
:has_condition => value
)
end

def update_condition(condition, value)
condition.update_attribute(:has_condition, value) unless condition.has_condition == value
end

belongs in model
def update

if( @medical_history.update_attributes(params[:medical_history]) &&
@medical_history.update_conditions(params[:conditions]) )
format.html {
format.js
else
format.js { render :text => "Error Updating History",
:status => :unprocessable_entity }
end
end
end

maybe a DB transaction? maybe nested params?

BUT REFACTORING MUST BE
DONE IN SMALL STEPS

RECAP: WINS

• improved controller action API

• intention-revealing method names communicate what’s occurring
at each stage of the update

• clean, testable public model API

3. IDENTIFY ENGINEERING
GOALS

“We’re going to push this nastiness down into the model. That
way we can get it tested, so we can more easily change it in
the future.”

Rate my talk: http://bit.ly/ajsharp-sunnyconf-refactoring

Slides: http://slidesha.re/ajsharp-sunnyconf-refactoring-slides

RESOURCES
• Talks/slides

• Rick Bradley’s railsconf slides: http://railsconf2010.rickbradley.com/

• Rick’s (beardless) hoedown 08 talk: http://tinyurl.com/ﬂogtalk

• Books

• Working Effectively with Legacy Code by Michael Feathers

• Refactoring: Ruby Edition by Jay Fields, Martin Fowler, et. al

• Domain Driven Design by Eric Evans

CONTACT

ajsharp@gmail.com
@ajsharp on twitter

Refactoring in Practice - Sunnyconf 2010

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Refactoring in Practice - Sunnyconf 2010