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rhandsontable.R

# How to capture data from rhandsontable after column addition/deletion, since 
# rhandsontable::hot_to_r() wouldn't work

# {rhandsontable} version ‘0.3.9’
# R version 4.2.0 (2022-04-22)

library(shiny)
library(rhandsontable)
library(data.table)
library(shinyjs)

# say this is your initial data.frame:
DF <- data.frame(
  val = 1:10, 
  bool = TRUE, 
  big = LETTERS[1:10],
  small = letters[1:10],
  dt = seq(from = Sys.Date(), by = "days", length.out = 10),
  stringsAsFactors = FALSE
)

ui <- fluidPage(
  shinyjs::useShinyjs(), 
  
  tags$h3(
    "This is my ui"
  ), 
  
  fluidRow(
    column(
      width = 12, 
      
      rHandsontableOutput("thistable")
    )
  )
)

server <- function(input, output, session) {
  output$thistable <- renderRHandsontable({
    rhandsontable(
      data = DF, 
      # set `useTypes = FALSE` to enable column addition:
      useTypes = FALSE
    ) |> 
      # allow col & row editing:
      hot_context_menu(
        allowColEdit = TRUE, allowRowEdit = TRUE
      )
  })
  
  # ---modal_newcolname---
  # after column addition, this modal let's user add new column name:
  modal_newcolname <- function(default_colname) {
    # default_colname is a string eg. newcol7 dependent on the tables ncols
    
    modalDialog(
      title = "Enter New Column Name:", 
      easyClose = FALSE, 
      
      fluidRow(
        column(
          width = 12, 
          align = "center", 
          
          textInput(
            inputId = "newcolname", 
            label = NULL, 
            value = default_colname
          )
        )
      ), 
      
      footer = actionButton(
        inputId = "done", label = "Done"
      )
    )
  }
  
  # disable `input$done` if `input$newcolname` is not given and also avoid
  # duplicate colnames:
  observe({
    shinyjs::toggleState(
      id = "done", 
      condition = {
        # newest column name:
        newestcolname <- paste0("newcol", length(rv_table$prevcolnames))
        # other column names:
        othercols <- rv_table$prevcolnames[
          rv_table$prevcolnames != newestcolname
        ]
        
        x <- input$newcolname
        
        # must be truthy:
        isTruthy(x) && 
          # must not be one of the other colnames:
          !(x %in% othercols)
      }
    )
  })
  
  # ---rv_table----
  # `reactiveValues()` obj to contain edited rhandsontable:
  rv_table <- reactiveValues(
    current = NULL, 
    # set prevcolnames to the names of the initial `DF`:
    prevcolnames = colnames(DF)
  )
  
  # ----changes----
  # On change of `input$thistable`:
  observeEvent(input$thistable, {
    # get current state of rhandsontable:
    current <- input$thistable$data
    
    current_dt <- lapply(current, FUN = function(x) {
      lapply(x, FUN = function(y) {
        # set NULL values to NA:
        y[is.null(y)] <- NA
        y
      })
    }) |> 
      # bind to a data.table:
      data.table::rbindlist(use.names = FALSE)
    
    # capture the event that occurred:
    event <- input$thistable$changes$event
    
    # On which index did the event occur:
    ind <- input$thistable$changes$ind + 1
    # Since rhandsontable uses JS and indexing starts at 0, I add the 1 to get 
    # normal R indices
    
    # if the event is addition/deletion of columns:
    if (event %in% c("afterCreateCol", "afterRemoveCol")) {
      # if event is column removal:
      if (identical(event, "afterRemoveCol")) {
        # reduce prevcolnames by 1:
        rv_table$prevcolnames <- rv_table$prevcolnames[-ind]
      }else {
        # if event is column creation:
        if (identical(event, "afterCreateCol")) {
          # new column name:
          newcolname <- paste0("newcol", ncol(current_dt))
          
          if (ind == 1) {
            # if column is added as the first one:
            # update prevcolnames:
            rv_table$prevcolnames <- c(newcolname, rv_table$prevcolnames)
          }else if (ind == ncol(current_dt)) {
            # if column is added as the last one:
            # update prevcolnames:
            rv_table$prevcolnames <- c(rv_table$prevcolnames, newcolname)
          }else {
            # if column is added in between other columns:
            # update prevcolnames:
            rv_table$prevcolnames <- append(
              x = rv_table$prevcolnames, 
              values = newcolname, 
              after = ind - 1
            )
          }
          
          # Trigger modal popup:
          showModal(modal_newcolname(default_colname = newcolname))
        }
      }
    }
    
    # finally set names for current_dt:
    setattr(
      x = current_dt, 
      name = "names", 
      value = rv_table$prevcolnames
    )
    
    # save current_dt in rv_table$current:
    rv_table$current <- current_dt
    
    print(current_dt)
  })
  
  # ---re-render----
  # rename the newest column to user's value:
  observeEvent(input$done, {
    # newest column name:
    newestcolname <- paste0("newcol", length(rv_table$prevcolnames))
    
    rv_table$prevcolnames[rv_table$prevcolnames == newestcolname] <- 
      input$newcolname
    
    removeModal(session = session)
  })
  
  # whenever there's an update on `rv_table$prevcolnames`, re-render the 
  # rhandsontable, but with isolated `rv_table$current` as the data:
  observeEvent(rv_table$prevcolnames, {
    req(rv_table$current)
    
    names(rv_table$current) <- rv_table$prevcolnames
    
    output$thistable <- renderRHandsontable({
      rhandsontable(
        data = isolate({ rv_table$current }),
        # set `useTypes = FALSE` to enable column addition:
        useTypes = FALSE
      ) |>
        # allow col & row editing:
        hot_context_menu(
          allowColEdit = TRUE, allowRowEdit = TRUE
        )
    })
  })
  
  # ----return----
  # now if you want to perform anything on the data after user edits, use this 
  # reactive:
  res <- reactive({
    rv_table$current
  })
}

shinyApp(ui, server)