R Shiny - unexpected behaviour of updateSelectizeInput with observer - r

Question

I have a selectizeInput that can take multiple values (here: names of datasets). The current state of this input is monitored by an observeEvent, which renders the corresponding datatables and dynamically populates a tabsetPanel with the outputs. It all works fine when I choose new values directly in the input field. However, when I supply multiple new values with the updateSelectizeInput function, all tabs contain the same dataframe corresponding to the last value in the selected argument.
The example below illustrates the problem. The UI reacts as expected when using the input field, but when pressing the "Add all at once" button all tabs contain the same dataframe.
library(shiny)
library(shinyWidgets)
library(shinyjs)
library(DT)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
selectizeInput(inputId = "dataframes", label = "select dataframes", choices = c("iris", "mtcars", "DNase", "ChickWeight"), multiple = TRUE),
actionButton(inputId = "add_all", label = "Add all at once")
),
mainPanel(tabsetPanel(id = "df_tabset"))
)
)
server <- function(input, output, session) {
tables <- reactiveValues(iris = iris, mtcars = mtcars, DNase = DNase, ChickWeight = ChickWeight,
df_tabset = NULL) # keeps track of currently displayed tables
observeEvent(input$dataframes, {
if (length(input$dataframes) > length(tables$df_tabset)) { # new dataframes are selected
new_dfs = setdiff(input$dataframes, tables$df_tabset)
for(df in new_dfs){
output[[df]] = renderDT(tables[[df]], editable = T, rownames = F, options = list(dom = "t")) # DOES NOT WORK AS EXPECTED IF THERE is > 1 NEW DF
appendTab(inputId = "df_tabset", select = TRUE,
tabPanel(title = df, value = df, DTOutput(outputId = df))
)
}
tables$df_tabset = input$dataframes # update
} else {
df = tables$df_tabset[! tables$df_tabset %in% input$dataframes]
removeTab(inputId = "df_tabset", target = df)
tables$df_tabset = input$dataframes
}
}, ignoreNULL = FALSE, ignoreInit = TRUE)
observeEvent(input$add_all, {
updateSelectizeInput(session, "dataframes", selected = c("iris", "mtcars", "DNase", "ChickWeight"))
})
}
shinyApp(ui = ui, server = server)

Answer 1

You have to use local (see here).
observeEvent(input$dataframes, {
if (length(input$dataframes) > length(tables$df_tabset)) { # new dataframes are selected
new_dfs = setdiff(input$dataframes, tables$df_tabset)
for(df in new_dfs){
local({
.df <- df
output[[.df]] = renderDT(tables[[.df]], editable = TRUE,
rownames = FALSE, options = list(dom = "t"))
})
appendTab(inputId = "df_tabset", select = TRUE,
tabPanel(title = df, value = df, DTOutput(outputId = df))
)
}
tables$df_tabset = input$dataframes # update
} else {
df = tables$df_tabset[! tables$df_tabset %in% input$dataframes]
removeTab(inputId = "df_tabset", target = df)
tables$df_tabset = input$dataframes
}
}, ignoreNULL = FALSE, ignoreInit = TRUE)