I have the observers working correctly in Example 1 code below, whereby clicking the "Click to show" button renders text and "Click to hide" hides the text. I am trying to extend this show/hide into more involved code in Example 2 below, whereby clicking "Delete" renders selectInput() to its right and clicking "Add" should hide that selectInput(). Clicking "Add" is not hiding selectInput(). Clicking "Delete" correctly renders the selectInput. There must be something wrong in my use of observeEvent() in Example 2 and I keep fiddling with it with no luck yet. Can someone please provide guidance on getting Example 2 to work like Example 1?

Example 1 code:

library(shiny)
library(shinyjs)

ui = fluidPage(
       useShinyjs(), # Set up shinyjs
       actionButton("btn", "Click to show"),
       actionButton("btn1","Click to hide"),
       hidden(p(id = "element", "I was invisible"))
     )

server = function(input, output) {
  observeEvent(input$btn, {show("element")})
  observeEvent(input$btn1,{hide("element")})
  }

shinyApp(ui,server)

Example 2 code:

library(rhandsontable)
library(shiny)
library(shinyjs)

mydata <- data.frame('Col 1' = c(1,24,0,1), check.names = FALSE)
rownames(mydata) <- c('Term A','Term B','Term C','Term D') 

ui <- fluidPage(
  useShinyjs(), # Set up shinyjs
  br(),
  rHandsontableOutput("mytable"),br(),
  fluidRow(
    column(1,actionButton("addCol", "Add",width = '70px')),
    column(1,actionButton("delCol","Delete",width = '70px')),
    column(3,hidden(p(id="element",uiOutput("delCol")))) # hide delCol output
    )
)

server <- function(input,output,session){
  
  output$mytable = renderRHandsontable(df())
  
  df <- eventReactive(input$addCol, {
    if(input$addCol > 0){
      newcol <- data.frame(mydata[,1])
      names(newcol) <- paste("Col",ncol(mydata) 1)
      mydata <<- cbind(mydata, newcol)
    }
    rhandsontable(mydata,rowHeaderWidth = 100, useTypes = TRUE)
  }, ignoreNULL = FALSE)
  
  observeEvent(input$delCol, priority = 0, {
    output$delCol<-renderUI(selectInput(
      "delCol",
      label=NULL,
      choices=colnames(mydata),
      selected="Col 1"))
  })
  
  observeEvent(input$addCol,priority = 1, {hide("element")}) # clicking addCol should hide delCol 
  
}

shinyApp(ui,server)

CodePudding user response：

You use "delCol" as

1. id of an actionButton
2. an uiOutput
3. id of an selectInput()

This causes problems we can avoid when giving unique names. I also don't think it is good style to have outputs inside of observeEvents. For this reason I separated the renderUi() from the observeEvent. The latter now only does the "hiding".

On a side note: I don't think it is a good idea to reassign mydata <<- cbind(mydata, newcol) in the global environment. It seems like you want to use a reactiveValues for that.

library(rhandsontable)
library(shiny)
library(shinyjs)

mydata <- data.frame('Col 1' = c(1,24,0,1), check.names = FALSE)
rownames(mydata) <- c('Term A','Term B','Term C','Term D') 

ui <- fluidPage(
  useShinyjs(), # Set up shinyjs
  br(),
  rHandsontableOutput("mytable"),br(),
  fluidRow(
    column(1,actionButton("addCol", "Add",width = '70px')),
    column(1,actionButton("delCol","Delete",width = '70px')),
    column(3, hidden(uiOutput("delCol2")))) # hide delCol output
  )
)

server <- function(input,output,session){
  
  output$mytable = renderRHandsontable(dat())
  
  dat <- eventReactive(input$addCol, {
    if(input$addCol > 0){
      newcol <- data.frame(mydata[,1])
      names(newcol) <- paste("Col",ncol(mydata) 1)
      mydata <<- cbind(mydata, newcol)
    }
    rhandsontable(mydata,rowHeaderWidth = 100, useTypes = TRUE)
  }, ignoreNULL = FALSE)
  
  observeEvent(input$delCol, priority = 0, show("delCol2"))
  # 
  observeEvent(input$addCol, priority = 1, hide("delCol2")) # clicking addCol should hide delCol
  
  output$delCol2 <-renderUI({
    selectInput(
      "delCol3",
      label=NULL,
      choices=colnames(mydata),
      selected="Col 1"
    )
  })
  
}

shinyApp(ui,server)