如何在Shiny应用中直接使用DESCRIPTION导入包及包内R文件夹函数？

1. Can I skip library() statements and use packages from DESCRIPTION's Imports? #

Absolutely, but it requires setting up your package's namespace correctly. Here's the breakdown:

• Explicit namespace references: If you don't import functions into your package's namespace, you can still use functions from your Imports packages by using the :: operator (e.g., shiny::fluidPage() instead of just fluidPage()). This avoids name conflicts and is the most straightforward approach for many cases.
• Importing into your package namespace: If you use roxygen2 tags like @import shiny (to pull in the entire package) or @importFrom shiny fluidPage renderPlot (to import specific functions), those functions become part of your package's namespace. When you run the Shiny app via your package's runExample() function, the app inherits this namespace—so you can call those functions directly without :: or library() calls.

Just adding packages to Imports in DESCRIPTION isn't enough; you need to define what's exposed in your package's NAMESPACE file (roxygen2 handles this automatically if you use the tags above).

2. Can the Shiny app recognize functions from my package's R folder without running devtools::load_all()? #

This depends entirely on how you launch the app:

• Running directly from the inst/shiny-examples/myapp folder: No, the app won't find your package's functions unless you've either installed the package (with devtools::install()) and loaded it via library(mypackage), or used devtools::load_all() to load the package into your current session.
• Running via an exported package function (like runExample()): Yes—once you've installed your package, calling mypackage::runExample() will run the app in a context where your package's functions are available. Your runExample() function should use system.file() to locate the app within the installed package, like this:

  runExample <- function() {
    shiny::runApp(system.file("shiny-examples/myapp", package = "mypackage"))
  }
  

  This way, the app inherits your package's namespace, so its functions are accessible without extra setup.

Quick dev tip: devtools::load_all() is still your friend during development—it lets you test changes to your package's functions without reinstalling the package every time.

内容的提问来源于stack exchange，提问作者azawalich