Save observer to user session — .save_observer • shinyCohortBuilder

The method used to store created observers (used to implement extra filter logic). The saved observer are then destroyed when filtering step is removed which prevents duplicated execution of accumulated observers.

Usage

.save_observer(observer, id, session)

Arguments

observer: An `observe` or `observeEvent` to be saved.
id: Id of the observer. Preferably prefixed with step_id. The saved observer is saved as `session$userData$observers[['<id>-observer']]` object.
session: Shiny session object.

Value

No return value, used for side effect which is saving the observer to `session$userData` object.

Examples

if (interactive()) {
  library(shiny)
  library(shinyCohortBuilder)

  ui <- fluidPage(
    numericInput("power", "Power", min = 0, max = 10, value = 1, step = 1),
    numericInput("value", "Value", min = 0, max = 100, value = 2, step = 0.1),
    actionButton("add", "Observe the selected power"),
    actionButton("rm", "Stop observing the selected power")
  )

  server <- function(input, output, session) {
    observeEvent(input$add, {
      .save_observer(
        observeEvent(input$value, {
           print(input$value ^ input$power)
        }),
        as.character(input$power),
        session = session
      )
    }, ignoreInit = TRUE)

    observeEvent(input$rm, {
      id <- paste0(input$power, "-observer")
      session$userData$observers[[id]]$destroy()
      session$userData$observers[[id]] <- NULL
    }, ignoreInit = TRUE)
  }

  shinyApp(ui, server)
}