shinybatch

{shinybatch} provides validated_reactive_val(), a hybrid reactive object that acts like a shiny::reactiveVal() but with a validation expression like a shiny::reactive(). This allows for the creation of self-validating reactive values, useful for managing complex, interdependent state in ‘shiny’ applications.

Motivation

In a standard Shiny app, you might have two inputs that depend on each other, like a “category” and “sub-category” selector. When the user changes the category, you need an observeEvent() to update the sub-category’s value to something valid. validated_reactive_val() simplifies this pattern by building the validation logic directly into the reactive object itself. We also ensure that the changes happen in the correct order, and prevent observers from “seeing” the inconsistent state.

# `group_val` depends on `input$level`.
group_val <- validated_reactive_val(
  value = "A1",
  validation_expr = {
    # If the current value is not valid for the new level, reset it.
    valid_groups <- if (input$level == "A") {
      c("A1", "A2")
    } else {
      c("B1", "B2")
    }
    if (.vrv() %in% valid_groups) {
      .vrv()
    } else {
      valid_groups[[1]]
    }
  }
)

Now, any time input$level changes, group_val() will automatically re-validate its own state. When you read group_val(), you are guaranteed to get a value that is consistent with its dependencies.

Installation

You can install the development version of shinybatch from GitHub with:

# install.packages("pak")
pak::pak("shinyworks/shinybatch")

Code of Conduct

Please note that the shinybatch project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.