airbnb/epoxy

Use default value from kotlin setter in a model view

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#598 opened on Oct 30, 2018

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 (3 comments) (0 reactions) (0 assignees)Java (8,412 stars) (738 forks)batch import
help wanted

Description

In @ModelView components setting default values is a pain, since the annotation @ModelProp has to take a string reference by name of a constant.

With kotlin's native support of default values, ideally the generated epoxy model could call a no-arg version of the setter to have the default value used.

The annotation processor and generated code would have to be updated for this. Main issues I see are having the annotation processor know if a default value is present (I think there is a kotlin metadata library we can use for that), and since the generated model is in java it needs to be able to access the no arg version of the function, so many jvmoverloads is required, but it would be nice to not need that

Contributor guide

Tech stack
kotlinjavaandroid
Domain
mobile
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Experience with Epoxy libraryUnderstanding of annotation processingKotlin language basicsFamiliarity with JVM overloads
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the Epoxy annotation processor codebase, specifically the handling of @ModelProp. Use the Kotlin metadata library to detect default values. Consider implementing a no arg setter call in the generated Java model class. Check if JvmOverloads annotation is required and how it interacts with the generated code. Look at existing issues or PRs related to Kotlin default values for guidance.