Shiny reports are awesome, but they sure do end up with many lines of code when adding lots of inputs and outputs. A ui.R file can rapidly exceed 50 lines of code and I prefer to keep things more compact. The best way I’ve found of doing that in other languages and in R is to modularise my code – break it down into independent chunks. Shiny already does this by having a server() and ui() section and allowing you to source other files.

The arguments for most of the shiny functions are ... which means you can pass it a list and it’ll parse all the items in the list. With this in mind, you can make list objects and use these instead of keeping all the individual components inline. Make a separate file that can be sourced within the server() section.

Here is a simple example using the single file demo code. It has a new file which holds the input controls (in this case a trivial single line, but it could be any number of them) and then references this before the server() and ui() components are executed.

This method should work, but there is another way of adding things to the environment for use by the ui.R file. You can utilise a global.R file.

Declutter a shiny report’s code
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What do you think?