And the not so glamorous back-end considerations for Shiny
The Parent-Child App Relationship
A common paradigm we’ve come across is the desire to create a Shiny app but have it used across different datasets with different scoped access to those datasets. It’s also common for the data to need some transformation prior to being used in the application. For these reasons we propose an opinionated paradigm of creating a package of Shiny modules, then using that package in child repositories, each with their own data.
Creating child repositories for each application instance solves the problem of changing and editing code in a single place, then persisting those changes to multiple endpoints, while still allowing for customization at the child application level. This is important in industries such as pharma because we can go through validation cycles and use certain versions of the parent package for some clinical studies, and experimental versions for others. It also allows for bug fixes in a central location, rather than forking a Shiny app and needing to make changes in multiple places.
A Consistent Data Structure
The child repository has an app.R file at the root level, and ui and server function that call modules from the parent. This doesn’t limit child applications to the parent structure, but the modules from the parent should assume as certain data structure to be used within the child applications. We propose creating a single object and storing it as data.rds. In the {matte} paradigm we create a jobs folder with a data_prep.Rmd - this takes the raw data needed for the application and manipulates it to be the generic structure needed for all apps. But what if your data is different between child repositories, you ask? We also include a meta.yaml file, a list of key value pairs for mapping columns to the application.
An Example
This can all seem very abstract, in inst/examples we’ve included an example of this paradigm:
parentpkg is a package with mod-chart and mod-table child1 is a shiny application that uses parentpkg’s modules as well as themeing with a data preperation file from mtcars child2 is a shiny application that uses iris
child1 and child2 look and feel like they come from the same ecosystem with the same branding, but this structure allows for further customization like including a third module custom to child2 that may not be in child1.
Can I use this with other Shiny frameworks?
Because the jobs endpoint is secondary to the application itself, you can use the {matte} paradigm with children applications that are Rhino, Golem, or native Shiny! The only limitation is that the parent application must be a package so that you can call it within the children.
Installation and Use
You can install the development version of matte from GitHub with:
# install.packages("devtools")
devtools::install_github("atorus-research/matte")