spatch
Spatch
Organize your logic into predictable, validated tasks.
Spatch is heavily inspired by ActiveInteraction and its precursor, Mutations.
Installation
Add this to your application's shard.yml
:
dependencies:
spatch:
github: calebuharrison/spatch
Then run:
shards install
Usage
require "spatch"
struct SayHello < Spatch::Task
input name : String
def perform
puts "Hello, #{name}!"
end
end
SayHello.run(name: "World")
Tasks
Task Structure
A task is a struct
that inherits from Spatch::Task
:
struct MyTask < Spatch::Task
# define your inputs and outputs here
def perform
# write your task logic here
end
end
Tasks are required to define a perform
method that gets indirectly called by the run
class method:
# Creates an instance of MyTask and performs it
MyTask.run
Inputs
Tasks can optionally define inputs using the input
macro:
struct SayFirstName < Spatch::Task
input first_name : String
def perform
puts @first_name
end
end
Note that an instance variable with the same name as the input is available for use inside the perform
method.
Now, if we want to run this task, we need to provide the required input:
SayFirstName.run(first_name: "Bob")
Of course, you can define as many inputs as you'd like:
struct CreateUser < Spatch::Task
input first_name : String
input last_name : String
input age : Int32
input email : String
def perform
User.new(@first_name, @last_name, @age, @email)
end
end
The run
method expects inputs in the order that they are defined. Of course, you can also use named arguments or a splatted NamedTuple
:
# All of these will work just fine
CreateUser.run("Bob", "McBobberson", 55, "bob@bob.bob")
CreateUser.run(age: 55, email: "bob@bob.bob", first_name: "Bob", last_name: "McBobberson")
params = { email: "bob@bob.bob", first_name: "Bob", last_name: "McBobberson", age: 55 }
CreateUser.run(**params)
This is all well and good, but I'm starting to have some reservations about the validity of that email address. You can define validation methods for your inputs:
struct SendEmail < Spatch::Task
input email : String
def validate_email
@issues.add "cannot end with bob" if @email.ends_with?("bob")
end
def perform
# send an email
end
end
When the run
method is called on SendEmail
, the email address will be validated before the perform
method is ever called:
# Invalid, email cannot end with bob. The `perform` method is never called.
SendEmail.run(email: "bob@bob.bob")
# Perfectly valid, it's a wonderful email address. The `perform` method is called.
SendEmail.run(email: "bob@bob.com")
An input is considered valid if no issues were added to it during validation. Multiple issues can be added to an input and all of them will be reported. In order for validation methods to be recognized and automatically run, they must be named after an input. Any issues added inside of a validation method will be associated with the input after which the method is named.
Outputs
The run
class method does not return the same thing that perform
returns. The perform
method's return value is discarded. Instead, task outputs can be defined using the output
macro:
struct CreateUser < Spatch::Task
input first_name : String
input last_name : String
input email : String
output user_id : Int32
output user_created_at : Time
def perform
user = User.create(@first_name, @last_name, @email)
@user_id = user.id
@user_created_at = user.created_at
end
end
Just like inputs, instance variables of the same name are created and exposed inside of the perform
method. By defining them as outputs, the task expects them to be populated with a value of the given type after perform
has been called. If outputs are not populated as expected, the task will fail and the offending outputs will be reported.
Summaries
When you call the run
class method on a task, it returns a Summary
:
summary = MyTask.run
A task is considered successful if:
- All inputs passed validation (no issues were added),
- There were no uncaught exceptions raised while executing the
perform
method, - Outputs were populated with values of the expected type at the end of the
perform
method.
You can ask a summary if the task was successful:
summary = MyTask.run
if summary.successful?
# celebrate
end
If the task was successful, then task outputs can be accessed directly via getter methods on the summary. For example, using our CreateUser
task above:
summary = CreateUser.run("Bob", "McBobberson", "bob@bob.com")
if summary.successful?
puts summary.user_id
puts summary.user_created_at
end
If the task was unsuccessful, then attempting to access its outputs will raise an exception. For this reason, you should always make sure to call successful?
before calling the output getters.
Anything that would cause a task to be considered unsuccessful is called an issue. You can retrieve issues from unsuccessful tasks by calling the issues
method on the task summary:
summary = CreateUser.run("Bob", "McBobberson", "bob@bob.bob")
if summary.successful?
# celebrate, access all of the outputs you want
else
puts summary.issues # => { :email => ["cannot end with bob"] }
end
Issues are added on a per-field basis. An uncaught exception during execution of the perform
method will be added as a :perform
issue.
There are some other handy methods available for summaries:
summary = CreateUser.run(...)
# Retrieve the time that this task began to run.
summary.began_at
# Retrieve the total runtime of the task.
summary.runtime
# Retrieve the time that this task finished.
summary.finished_at
Contributing
- Fork it ( https://github.com/calebuharrison/spatch/fork )
- Create your feature branch (git checkout -b my-new-feature)
- Commit your changes (git commit -am 'Add some feature')
- Push to the branch (git push origin my-new-feature)
- Create a new Pull Request
Contributors
- calebuharrison Caleb Harrison - creator, maintainer
spatch
- 0
- 0
- 0
- 0
- 0
- almost 7 years ago
- January 30, 2018
MIT License
Fri, 22 Nov 2024 11:52:07 GMT