Avoiding the mud - Speaker Deck

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avoiding the mud

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richard miller @mr_r_miller richardmiller.co.uk sensiolabs uk

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http://www.ﬂickr.com/photos/brostad/8583990904

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what makes an application fragile?

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single responsibility principle

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a class or module should have one, and only one, reason to change

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dependency inversion principle

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High-level modules should not depend on low-level modules

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Both should depend on abstractions.

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should everything go in a bundle?

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no (imo)

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HumanResourcesBundle

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HumanResourcesBundle HumanResources responsible for framework related code responsible for domain related code

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HumanResourcesBundle HumanResources

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better?

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still tightly coupled

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AbsenceEntity Request Absence Form Cancel Absence Form Approve Absence Form Change Absence Type Form

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entities coupled to forms

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complex validation

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form events

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entity is responsible for validating user input

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AbsenceEntity Request Absence Form Cancel Absence Form Approve Absence Form Change Absence Type Form Request Absence Command Cancel Absence Command Approve Absence Command Change Absence Type Command

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simpler validation

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command name captures the domain action

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but more classes!

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simpler classes

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repetition?

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technical complexity reduced

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what else?

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entities coupled to templates

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AbsenceEntity upcoming .html .twig details .html .twig calendar .html .twig unapproved .html .twig

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logic in templates

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{% if absence.endDate < date() %} past {% else %} absence.status {% endif %} getDisplayStatus() AbsenceEntity getEndDate() getStatus()

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if in php method it could be tested

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so let's move it to the entity

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getDisplayStatus() AbsenceEntity getEndDate() getStatus() getDisplayStatus() {{ absence.displayStatus }}

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but presentational logic is not a domain responsibility

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AbsenceEntity Request Absence Form Cancel Absence Form Approve Absence Form Change Absence Type Form Absence View upcoming .html .twig details .html .twig calendar .html .twig unapproved .html .twig getStatus()

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commands are now responsible for capturing data for an action

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views are responsible for providing data for presentation

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so what is our entity responsible for?

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Request Absence Controller Absence Entity setReason($reason) setStatus(AbsenceEntity::CANCELLED) setCancellationDate(new DateTime()) Cancel Absence Command getReason()

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the controller is responsible for state in the model

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Request Absence Controller Absence Entity cancel($reason) Cancel Absence Command getReason()

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the entity now protects its state

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it exposes behaviours instead

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Cancel Absence Command Absence Entity Validate internal consistency Validate user input

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Request Absence Controller Absence Entity cancel($reason) Cancel Absence Command getReason()

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AbsenceEntity cancel($reason) Cancel Absence Command Handler Request Absence Controller Absence Entity cancel($reason) Cancel Absence Command

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infrastructure?

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persistence is not a domain responsibility

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but the repository is part of the domain

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Absences (Interface) findById($id) findUpcomingByMember($member) findAllByMember($member) Doctrine ORM Absence Repository Doctrine ODM Absence Repository Guzzle Client Absence Repository Infrastructure Domain

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AbsenceEntity Absences Domain Bundle Service Conﬁg Infrastructure Doctrine ORM Absence Repository Mapping Conﬁg

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Absences findById($id) findUpcomingByMember($member) findAllByMember($member) add(AbsenceEntity $absence)

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how often is persistence changed?

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doctrine events

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OnUpdate Event AbsenceEntity Dispatches

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doctrine domain events

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OnUpdate Event AbsenceEntity Dispatches

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Absence Cancelled Event Cancel Absence Command Handler Dispatches

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what bundles should I have?

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how big should they be?

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maybe just one

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don't split if they will be coupled anyway

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so could be quite big

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split out code reusable in other applications

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HumanResources CustomLoggingBundle HumanResourcesBundle

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HumanResourcesBundle HumanResources CustomLoggingBundle CustomLogging CustomLoggingBundle CustomLoggingBundle CustomLogging HumanResourcesBundle

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HumanResources CustomLoggingBundle CustomLogging CustomLoggingBundle CustomLoggingBundle CustomLogging HumanResourcesBundle

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so could be quite small

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split application bundles when domain is big enough to split

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and can be decoupled

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AbsencePlannerBundle AbsencePlanner CustomLoggingBundle CustomLogging CustomLoggingBundle RecruitmentBundle Recruitment

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Message Queue/REST AbsencePlannerBundle AbsencePlanner CustomLoggingBundle CustomLogging CustomLoggingBundle RecruitmentBundle Recruitment

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anything else to split out?

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AbsencePlannerBundle AbsencePlanner RecruitmentBundle Recruitment AbsencePlannerBundle AbsencePlanner CustomLoggingBundle CustomLogging CustomLoggingBundle RecruitmentBundle Recruitment User Management

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!= Staff Member Entity User Entity

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AbsencePlannerBundle AbsencePlanner AbsencePlannerBundle AbsencePlanner CustomLoggingBundle CustomLogging CustomLoggingBundle RecruitmentBundle Recruitment UserManagementBundle