R Shiny DT auto generate a value in a newly added row

[Arthur_Morgan]

I have a Shiny app that allows the user to enter their project details to the database. This is achieved by the Add Project Details Button that adds an empty row to the table. Now the next step is:

• When the add button is clicked the app auto generates the next reference number (under column Reference.Number) in the new row based on the previous one. So, like based on the sample data below since the last reference number is 33335, the next reference number would be 33336. And if another row is added then it will be 33337.

How can I do this?

Sample Data (df):

structure(list(Reference.Number = c("33331", "33332", "33333", 
"33334", "33335"), Request.Date = c("1/6/2022", "1/6/2022", "1/19/2022", 
"1/20/2021", "1/24/2022"), Requestor.Name = c("Comm Dist 3 by Kitty", 
"Comm Dist 3 by Kitty", "Updated maps for David", 
"    Stone Cold", "Updated SOE 60 inch wall map"), Requestor.Dept.Div = c("C 3 Staff", 
"C 3 Staff", "Unincorp & Comm", "Mt.Rushmore AME Church Ft. Billy", 
"SOE"), Requestor.Phone = c("", "", "", "", ""), Contact.Person = c("Tommy", 
"Tommy", "Bob", "Bob", "Joe"), Contact.Phone = c("1111", 
"2222", "3333", "ext 1111", "3434"), Deadline = c("1/20/2022", 
"1/20/2022", "1/22/2022", "", "1/24/2022"), Project.Description = c("45x36 portrait map ", 
"45x36 portrait map  ", 
"24x24 Unincorporated areas, "Percent Females Aged 25 - 55  Below Poverty Level By Zip Code", 
"SOE Wall Map 60x60 p), Project.File.Location = c("", 
"", "C:\\ABC\\Tommy\\work|Map-Projects\\BD Unincororated\\#14785 Unincorporated 24x24.pdf", 
"C:\\ABC\\Demographics\\Demographic_Request\\FemalesAge10-18BelowPoveryLevel\\FemalesAge10-18BelowPoveryLevel.aprx", 
"C:\\ABC\\Tommy\\work|Map-Projects\\BD Unincororated\\#14786 V P 60x60.pdf"
), PDF.File.....Map.Name.... = c("", "", "", "C:\\ABC\\Demographics\\Demographic_Request\\FemalesAge10-18BelowPoveryLevel\\pdfs\\MapNo14785.pdf", 
""), Assigned.To = c("", "", "", "", ""), Completion.Date = c("", 
"", "", "", ""), Notes = c(NA, NA, NA, NA, NA), Year = c(2022, 
2022, 2022, 2022, 2022)), class = "data.frame", row.names = c(NA, -5L)) 

Code:

library(shiny)
library(shinythemes)
library(shinyWidgets)
library(shinyanimate)
library(DT)
library(tidyverse)

# Define UI for application that draws a histogram
ui =   navbarPage(tags$style("table, .table {color: unset;} .dataTable th, .datatables input {color: white}"),
                  title = div("GIS Team Projects"),
                  theme = shinytheme("cyborg"),
                  tabPanel("GIS Projects",
                           icon = icon("info"),
                           div(p(h1("Instructions:"),style="text-align: justify;")),
                           p("1. The user can add their project details.", style="color:black"),
                           uiOutput("all"),
                  sidebarLayout(
                    sidebarPanel(
                      actionButton("addData", "Add Project Details"),
                      ),
                    mainPanel(
                      downloadButton("download1","Download data as csv"),                
                      DTOutput("contents")),)
                    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

  myData = df
  
  # Create an 'empty' tibble 
   user_table =
     myData %>% 
      slice(1) %>% 
    # Transpose the first row of test into two columns
    gather(key = "column_name", value = "value") %>%
    # Replace all values with ""
    mutate(value = "") %>%
    # Reshape the data from long to wide
    spread(column_name, value) %>%
    # Rearrange the column order to match that of test
    select(colnames(myData))
   
   # Display data as is
   output$contents =
     renderDT(myData,
              server = FALSE,
              editable = TRUE,
              options = list(lengthChange = TRUE),
              rownames = FALSE)
   
   # Store a proxy of contents 
   proxy = dataTableProxy(outputId = "contents")
   
   # Each time addData is pressed, add user_table to proxy
   observeEvent(eventExpr = input$addData, {
     proxy %>% 
       addRow(user_table)
   })
  
}

# Run the application 
shinyApp(ui = ui, server = server)