Dry::Transaction Paul Sadauskas RubyConf Denver 2021

Hi! Paul Sadauskas Lead Architect at TextUs ● github.com/paul ● @theamazingrando Like everyone else, we’re hiring! https://textus.com/jobs This is the talk that made me want to join TextUs — Jason Taylor Ruby on Rails Podcast Ep 389, Oct 27 2021

The Problem Model Controller Where do I put my business logic?

Service Objects ● Adapter ● Command ● Decorator ● Query Object ● View Model ● Presenter ● Form Object https://refactoring.guru

Command Pattern The Command Pattern creates objects which encapsulate actions and parameters

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Dry-rb

Dry::Transaction Dry::Transaction is a business transaction DSL. It provides a simple way to define a complex business transaction that includes processing over many steps and by many different objects. It makes error handling a primary concern by taking a “Railway Oriented Programming” approach to capturing and returning errors from any step in the transaction. ● A business transaction is a series of operations where any can fail and stop the processing. ● A business transaction may resolve its operations using an external container. ● A business transaction can describe its steps on an abstract level without being coupled to any details about how individual operations work. ● A business transaction doesn’t have any state. ● Each operation shouldn’t accumulate state, instead it should receive an input and return an output without causing any side-effects. ● The only interface of an operation is #call(input). ● Each operation provides a meaningful piece of functionality and can be reused. ● Errors in any operation should be easily caught and handled as part of the normal application flow. — From the Dry-Transaction documentation

Anatomy of a Transaction ● Each “step” is run in the order declared in the `step` DSL ● Each step returns a “Result”, which is “Success” or “Failure” ● If Success, it gets passed to the next step ● If Failure, execution halts, no more steps are run, and that Failure is returned.

Monads Monads are monoids in the category of endofunctors. -- Wikipedia or something

Maybe Monad A wrapper than can contain only two possible items: ● Just/Some - wraps the value ● Nothing/None - when the value is missing Monad Presence Absence Haskell/Elm Maybe Just Nothing Rust Option Some None Dry::Monad Maybe Some None

Maybe Monad

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Maybe #bind Some: ● Yields its value to the block ● Block must return a Maybe ● Returns the result of the block None: ● Doesn’t call the block ● Returns self

Maybe #fmap Some: ● Similar to bind ● Block doesn’t return a monad ● (fmap wraps block result in one) None: ● Same as bind ● Doesn’t call the block

Maybe #value_or Safe way to extract a value or default Some: ● Doesn’t call block ● Returns value None: ● Calls block

Maybe helpers

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Result Monad

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Step Adapters “Normal” step Step adapters (try and map)

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Error Handling

Error handling

Error handling — Matcher DSL

Error handling — Matcher DSL

Error handling — Matcher DSL

Testing

Testing — Step Injection

Testing — Step injection

Custom Step Adapters

Custom Step Adapters

Custom Step Adapter - Merge

Custom Step Adapter - Validate

Custom Step Adapter - Other Useful Ones We Wrote

Bye! Paul Sadauskas Lead Architect at TextUs ● github.com/paul ● @theamazingrando Like everyone else, we’re hiring! https://textus.com/jobs This is the talk that made me want to join TextUs — Jason Taylor Ruby on Rails Podcast Ep 389, Oct 27 2021