When Rails presenters are a smell and what to do about it

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When Rails presenters are a smell and what to do about it Andrzej Krzywda @andrzejkrzywda

Transcript of When Rails presenters are a smell and what to do about it

Page 1: When Rails presenters are a smell and what to do about it

When Rails presenters are a smell and what to

do about itAndrzej Krzywda @andrzejkrzywda

Page 2: When Rails presenters are a smell and what to do about it

helpers presenters

???

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Presenters

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Remarks

• takes multiple AR objects

• uses the exposed AR state

• returns a hash

• some repetition solved by meta

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Remarks

• includes url_helpers

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What’s good?

• no need for helpers

• view logic in one place

• better OOP than helpers

• handles non-CRUD views quite well

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What’s bad?• ActiveRecord all the way down

• access attributes

• even when we pass domain POROs

• tell, don’t ask

• coupling to AR or POROs

• potentially slow

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Are there any alternatives to presenters?

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Read models

CQRS DDD

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Example

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We need events(or maybe not)

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rails_event_store

The fastest way to get events in your ugly Rails apps

https://github.com/arkency/rails_event_store

https://github.com/arkency/rails_event_store
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What to do with the past events?

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1. RankingHadState 2. turn existing data into events

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What if I don’t want events?

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Enjoy the coupling and call the read model

directly

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Read models• Event handlers

• Customized for the view

• denormalized / derived data

• easy to rebuild

• cache-like

• tell, don’t ask

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When to choose read models over presenters?

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Choose presenters

• When your app is still very CRUDish

• what you create is what you list

• No goal to escape AR

• No performance problems

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Choose read models

• Performance

• When you prefer domain objects not to leak attributes

• show data from different modules

• gateway drug to DDD/CQRS

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Read it online

http://blog.arkency.com/2015/05/introducing-read-models-in-your-legacy-application/

http://blog.arkency.com/2015/05/introducing-read-models-in-your-legacy-application/
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Thanks!


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