How to write a MODULE with two textInputs, in which input in one, blanks out the other and vv? - module

Question

I want to write a MODULE where the client function returns a taglist with 2 textInputs. The user can enter a value in either textInput 1 or textInput 2 but not both. In other words, one textInput excludes the other, emulating a set of radio buttons.
Hence, the server function should observe the input in such a way that if the user enters a value in textInput 1, then textInput 2 is made blank and vice versa.
Also, the server function returns a dataframe with the values in the textInputs, i.e. either data.frame (one = enteredValue, two = NA) or data.frame (one = NA, two = enteredValue)
As we are planning on using this two-textInput widget in many of our shiny apps, I really want to make it a module. It seems like a simple thing to implement, but so far I have not been successful. (My experience is that observe, observeEvent, and eventReactive work differently in modules than in regular apps)
Any ideas to point me in the right direction are welcome.

Answer 1

I believe eventReactive and observeEvent work inside of a Shiny module. I've created a small module that basically does what you describe.
ui.R
library(shiny)
library(shinydashboard)
source("doubleField.R")
shinyUI(dashboardPage(
dashboardHeader(title = "Test"),
dashboardSidebar(disable = T),
dashboardBody(
doubleFieldUI("fields"),
fluidRow(
dataTableOutput("outputTable")
)
)
))
server.R
library(shiny)
source("doubleField.R")
shinyServer(function(input, output) {
fields <- callModule(doubleField, "fields")
output$outputTable <- renderDataTable(fields())
})
doubleField.R
library(stringr)
doubleFieldUI <- function(id) {
ns <- NS(id)
return(
tagList(
fluidRow(
column(width = 6, textInput(ns("fieldA"), "Field A")),
column(width = 6, textInput(ns("fieldB"), "Field B"))
),
fluidRow(
column(width = 2, "Output: "),
column(width = 4, textOutput(ns("outputValue")))
)
)
)
}
is_empty_string <- function(s) {
return(str_length(s) == 0)
}
doubleField <- function(input, output, session) {
valueA <- eventReactive(input$fieldA, {
if(!is_empty_string(input$fieldA)) {
ns <- session$ns
updateTextInput(session, "fieldB", value = "")
return(input$fieldA)
}
return("")
})
valueB <- eventReactive(input$fieldB, {
if(!is_empty_string(input$fieldB)) {
ns <- session$ns
updateTextInput(session, "fieldA", value = "")
return(input$fieldB)
}
return("")
})
value <- reactive({
values <- c(input$fieldA, input$fieldB)
return(values[which(!is_empty_string(values))])
})
output$outputValue <- renderText({
value()
})
result_df <- reactive({
v_A <- valueA()
v_B <- valueB()
df <- data.frame(
list(
"valueA" = ifelse(is_empty_string(v_A), NULL, v_A),
"valueB" = ifelse(is_empty_string(v_B), NULL, v_B)
)
)
return(df)
})
return(result_df);
}
I hope this helps getting you started.