CODEWITHSUNDEEP
rshinyreactive
Jaccar
Jaccar

Reputation: 1844

Get "error: could not find function" in Shiny relating to reactive expression

I am trying to return a character vector created in a reactive expression in Shiny. However, when I run the app, I get the following:

Error: could not find function "check_case"

check_case is a reactive expression, not a function.

I can see a number of questions from people with similar issues, but the answers don't seem to fit this (for e.g., missing parentheses when calling reactive expression; calling something that hasn't been returned in the reactive expression).

I've tried immediately translating check_case() into a character vector in the output before using paste. I have also tried adding more arguments to paste so it includes sep = and collapse =, in case this is part of the issue, but this doesn't change the result I'm getting.

I currently have two theories:

Code: 

library(shiny)
library(shinydashboard)


sidebar <- dashboardSidebar(
  selectInput(
  "case_select", label = "Select case",
  choices = c("Upper", "Lower")
  )
)

body <- dashboardBody(
  fluidRow(
      htmlOutput("text"))
)

ui <- dashboardPage(dashboardHeader(title = "Example"),
                    sidebar,
                    body
)

server <- function(input, output) {

  output$check_case <- reactive({
    if (input$case_select == "Upper") {
      case_list <- c("A", "B", "C")
      } else {
        case_list <- c("a", "b", "c")
      }
    return(case_list)
  })

  output$text <- renderUI({
    check_case <- check_case()
    HTML(paste(check_case, sep = "", collapse = ""))
  })
}

Upvotes: 4

Views: 5813

Answers (1)

Chabo
Chabo

Reputation: 3000

The issue is regarding the fact you are trying to output a reactive variable while also creating it. It is also important to note that you need to output to an existing UI element when rendering.

This can simply be solved by creating the reactive varaible, and then subsequently rendering it with renderUI as you are doing with ouput$text

server <- function(input, output) {

  check_case <- reactive({
    if (input$case_select == "Upper") {
      case_list <- c("A", "B", "C")
      } else {
        case_list <- c("a", "b", "c")
      }
    return(case_list)
  })

  output$text <- renderUI({
    check_case <- check_case()
    HTML(paste(check_case, sep = "", collapse = ""))
  })
}

Just a simple error

Upvotes: 3

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