olleharstedt / seq

Small PHP experiment for enforce imperative shell

Test of command object queue as a way to lift out side-effects, making functions more testable that way.

Compare: Functional core, imperative shell

Purpose: Extend the functional core even when side-effects are entangled with business logic

que

• Since not all side-effects have to happen at once, you can install a queue that runs at app shutdown
• Usage: que(fn () => ...)
• Whatever is in the queue is executed, in order of definition, at app shutdown

run

• run is used when you need the result of a side-effect immediately
• During mocking, you give run a configuration object to tell it what to return

seq

• When a side-effect depends on the result of a previous side-effect, e.g. create file if it doesn't already exist, you can sequence closures together
• This is like chaining promises together; "do this, then this if success, then this if success"

Survey activator

• Flush cache
• Fire event "beforeSurveyActivate"
• Calculate field map
• Create response database table
• Create survey folder
• Set survey active = 'Y'
• Fire event "afterSurveyActivate"

Notes

• The outmost shell is at script or app shutdown - run queue at that point?
• Sacrificing performance for testability
• How is composability affected?