grapes-set-grapes: Destructure a named list into individual variables

In Appsilon/rhino: A Framework for Enterprise Shiny Applications

Destructure a named list into individual variables

Description

The destructuring operator ⁠%<-%⁠ allows you to extract multiple named values from a list into individual variables in a single assignment. This provides a convenient way to unpack list elements by name.

While it works with any named list, it was primarily designed to improve the ergonomics of working with Shiny modules that return multiple reactive values. Instead of manually assigning each reactive value from a module's return list, you can destructure them all at once.

Usage

lhs %<-% rhs

Arguments

lhs	A call to c() containing variable names to assign to. All variable names should exist in the rhs list.
rhs	A named list containing the values to assign

Value

Invisibly returns the right-hand side list

Examples

# Basic destructuring
data <- list(x = 1, y = 2, z = 3)
c(x, y) %<-% data
x  # 1
y  # 2

# Works with unsorted names
result <- list(last = "Smith", first = "John")
c(first, last) %<-% result

# Shiny module example
if (interactive()) {
  module_server <- function(id) {
    shiny::moduleServer(id, function(input, output, session) {
      list(
        value = shiny::reactive(input$num),
        text = shiny::reactive(input$txt)
      )
    })
  }

  # Clean extraction of reactive values
  c(value, text) %<-% module_server("my_module")
}

# Can be used with pipe operations
# Note: The piped expression must be wrapped in brackets
## Not run: 
c(value) %<-% (
  123 |>
    list(value = _)
)

## End(Not run)

Appsilon/rhino documentation built on April 14, 2025, 7:07 p.m.