Sequentially Generating a Dynamic User Interface in Shiny, R - r

Question

I've created a dynamic user interface in R which generates four selectizeInput boxes within a fluid row environment with a matching set of observers watching for input. If an addFilter button is selected, then an additional fluid row is generated with another four boxes.
My issue surrounds the saving of previously inputted values. I have a group of reactive values storing the user inputs. These values are then inputted into the observers on the updateselectize. If a user clicks slowly, it all works fine. However, if a user clicks quickly, sometimes the values are erased.
I believe this happens because by the time the script comes to setting up the new interface, the old one with observers hasn't quite been rendered; but the values have been reset.
Below is a MWE. Note that to trigger the bug, you need to double click on the Add Filter button quickly.
Server.R:
library(shiny)
shinyServer(function(session, input, output) {
rValues <- reactiveValues(filter_counter = 1, filter_counter2 = 1, filter_waiter = 1, savedFil_1 = "", savedOp_1 = "",
savedCrit_1 = "", savedAO_1 = "")
columns <- c("C1", "C2")
operators <- c("O1", "O2")
values <- c("V1", "V2")
andor <- c("&&", "||")
observeEvent(input$AddFilter,{
if (rValues[['filter_waiter']] == 1) {
# Step 1: Store
lapply(1:rValues$filter_counter, function(i) {
rValues[[paste0("savedFil_", i)]] <- input[[paste0("fil_", i)]]
rValues[[paste0("savedOp_", i)]] <- input[[paste0("filOperators_", i)]]
rValues[[paste0("savedCrit_", i)]] <- input[[paste0("filCriteria_", i)]]
rValues[[paste0("savedAO_", i)]] <- input[[paste0("andor_", i)]]
})
# Step 2: Increment counter
rValues$filter_counter <- rValues$filter_counter + 1
# Step 3: Set filter waiter
rValues[['filter_waiter']] <- 0
}
})
output$filters <- renderUI({
if (rValues[['filter_waiter']] == 1) {
ui <- lapply(1:rValues$filter_counter, function(i) {
fluidRow(
column(4, selectizeInput(paste0("fil_", i), label = NULL, choices = NULL)),
column(2, selectizeInput(paste0("filOperators_", i), label = NULL, choices = NULL)),
column(4, selectizeInput(paste0("filCriteria_", i), label = NULL, choices = NULL)),
column(2, selectizeInput(paste0("andor_", i), label = NULL, choices = NULL)))
})
return(ui)
}
})
### Create observers for filters
observe({
lapply(1:rValues$filter_counter, function(i){
# Update the Selectizes
updateSelectizeInput(session, paste0("fil_", i), selected = rValues[[paste0("savedFil_", i)]], choices = columns, server = TRUE)
updateSelectizeInput(session, paste0("filOperators_", i), selected = rValues[[paste0("savedOp_", i)]], choices = operators, server = TRUE)
updateSelectizeInput(session, paste0("filCriteria_", i), selected = rValues[[paste0("savedCrit_", i)]], choices = values, server = TRUE)
updateSelectizeInput(session, paste0("andor_", i), selected = rValues[[paste0("savedAO_", i)]], choices = c("", "&&", "||"), server = TRUE)
})
rValues[['filter_waiter']] <- 1
})
})
And the UI.R:
library(shiny)
shinyUI(fluidPage(
# Application title
titlePanel("Dynamic SelectizeInput UI"),
sidebarLayout(
sidebarPanel(
actionButton("AddFilter", label = "Add a Filter"),
uiOutput("filters")
),
mainPanel(
h1("")
)
)
))

Answer 1

Your code can be simplified. Yo do not need to update the selectizeInput controls as you are generating new controls each time the button is selected.
You have too many reactive variables. I change to global variables. If you do not want to use global variables, then use reactive variables with isolate.
library(shiny)
filter_counter <- 0
filter_values <- list()
columns <- c("C1", "C2")
operators <- c("O1", "O2")
values <- c("V1", "V2")
andor <- c("&&", "||")
server<- shinyServer(function(session, input, output) {
output$filters <- renderUI({
input$AddFilter
# Step 1: store filter values
if ( filter_counter>0) {
lapply(1:filter_counter, function(i) {
filter_values[[paste0("savedFil_", i)]] <<- input[[paste0("fil_", i)]]
filter_values[[paste0("savedOp_", i)]] <<- input[[paste0("filOperators_", i)]]
filter_values[[paste0("savedCrit_", i)]] <<- input[[paste0("filCriteria_", i)]]
filter_values[[paste0("savedAO_", i)]] <<- input[[paste0("andor_", i)]]
})
}
# Step 2: Increment counter
filter_counter <<- filter_counter + 1
# Step 3: generate selectInputs
ui <- lapply(1:filter_counter, function(i){
fluidRow(
column(4,selectizeInput(paste0("fil_", i), label= 'fil', selected = filter_values[[paste0("savedFil_", i)]], choices = columns )),
column(2,selectizeInput(paste0("filOperators_", i),label= 'filop', selected = filter_values[[paste0("savedOp_", i)]], choices = operators )),
column(4,selectizeInput(paste0("filCriteria_", i),label= 'filcri', selected = filter_values[[paste0("savedCrit_", i)]], choices = values )),
column(2,selectizeInput(paste0("andor_", i),label= 'andor', selected = filter_values[[paste0("savedAO_", i)]], choices = c("", "&&", "||") ))
)
})
})
})
ui <- shinyUI(fluidPage(
# Application title
titlePanel("Dynamic SelectizeInput UI"),
sidebarLayout(
sidebarPanel(
actionButton("AddFilter", label = "Add a Filter"),
uiOutput("filters")
),
mainPanel(
h1("")
)
)
))
shinyApp(ui , server)