How to combine multiple inputs in one vector in shiny. Number of inputs depends on user's choice

Question

I'm trying to create an UI in which user can choose some objects (as many as they want) and their respective weights. The weight input fields appear only when there's more than one object and increase as the user selects more objects. This part already works.

What I need is a vector that holds all the weights saved in the w1, w2 and so on.

I've tried using for loops and sapply with get() function but can't access the input$w1, input$w2 etc.

library(shiny)

# Create list of objects
object_list <- vector()
object_list <- paste0("O_", 1:10)
names(object_list) <- paste("Object", 1:10)

ui <- dashboardPage(
  dashboardHeader(title = "Dynamic UI"),
  dashboardSidebar(
    width = 700,
    fluidRow(
      column(7, selectInput("chosen_objects", "Chosen objects", choices = object_list, multiple = TRUE, width = "100%")),
      column(5, uiOutput("weights"))
    )
  ),
  dashboardBody(
    fluidPage(tabBox(width=2500,
                     tabPanel(
                       title = "Table"
                      )
    )
    )
  )
)

server <- function(input,output) {

  objects_number <- reactive({length(input$chosen_objects)})

  output$weights <- renderUI({
    if (is.na(objects_number()) | objects_number() <= 1)
      return(NULL)
    lapply(1:objects_number(), function(i) {
      id <- paste0("w", i)
      textInput(id, paste("Weight of", input$chosen_objects[i]), value = input[[id]], width = "50%", placeholder = "%")
    })
  })

}

shinyApp(ui, server)

Is there a way to collect the dynamic inputs in one vector or list?

Answer 1

I have made a few changes and based on your code I think you are good enough to see and get them by yourself. Let me know if you have any questions -

library(shiny)

# Create list of objects
object_list <- vector()
object_list <- paste0("O_", 1:10)
names(object_list) <- paste("Object", 1:10)

ui <- dashboardPage(
  dashboardHeader(title = "Dynamic UI"),
  dashboardSidebar(
    width = 700,
    fluidRow(
      column(7, selectInput("chosen_objects", "Chosen objects", 
                     choices = object_list, multiple = TRUE, width = "100%")),
      column(5, uiOutput("weights"))
    )
  ),
  dashboardBody(
    fluidPage(tabBox(width=2500,
                     tabPanel(
                       title = "Table",
                       verbatimTextOutput("weight_output")
                      )
    )
    )
  )
)

server <- function(input,output) {

  objects_number <- reactive({length(input$chosen_objects)})

  output$weights <- renderUI({
    if (is.na(objects_number()) | objects_number() <= 1)
      return(NULL)
    lapply(gsub("[A-Z]+_", "", input$chosen_objects), function(i) {
      id <- paste0("w", i)
      textInput(id, paste("Weight of", paste0("O_", i)), 
                value = NULL, width = "50%", placeholder = "%")
    })
  })

  output$weight_output <- renderPrint({
    req(input$chosen_objects)
    sapply(paste0("w", gsub("[A-Z]+_", "", input$chosen_objects)), function(a) input[[a]])
  })

}

shinyApp(ui, server)