Refreshing Filter and Table - r

Question

I have the following code:
library(shiny)
library(shinydashboard)
library(rhandsontable)
header <- dashboardHeader(title = "Sample", titleWidth = 375)
sidebar <- dashboardSidebar(width = 270,
sidebarMenu(id="mymenu",
menuItem(text = "Home", tabName = "tabCars", icon = icon("home", class="home"))
))
body <- dashboardBody (
tabItems(
tabItem(tabName = "tabCars",
fluidRow(
column(width = 2,
selectInput(
inputId = "selected_CarCylinders",
label = "Car Cylinders",
choices = mtcars$cyl,
selectize = TRUE,
width = "250px",
multiple = FALSE
)),
column(width = 2, style = "margin-top: 25px",
actionButton("deleteBtn", "Delete Selected Cylinders")),
column(width = 1, style = "margin-top: 25px",
actionButton("refreshBtn", "Refresh Filter/Chart")),
rHandsontableOutput("carDT")
)
)
)
)
ui <- dashboardPage(header, sidebar, body)
server <- function(input, output, session) {
output$carDT <- renderRHandsontable({
df <- mtcars
rhandsontable(df, stretchH = "all")
})
observeEvent(input$deleteBtn, {
# need help here
})
observeEvent(input$refreshBtn, {
# need help here
})
}
shinyApp(ui, server)
I need help writing what would go into the input$deleteBtn and input$refreshBtn sections of the server side. If you run the code as is, the idea is to select the number of cylinders from mtcars, then click the Delete button to remove all those entries from the table and filter; however, the filter and table would only update after clicking the refresh button.

Answer 1

While permanently delete screams a SQLite database to me, you could achieve this by using a reactiveVal to store the dataframe and call req to only refresh the table when you click the refreshBtn (in this case, you also have to click it to display the table at the start of the app).
server <- function(input, output, session) {
# Create a `reactiveVal` and set a value to it
df <- reactiveVal()
df(mtcars)
output$carDT <- renderRHandsontable({
req(input$refreshBtn)
rhandsontable(df(), stretchH = "all")
})
observeEvent(input$deleteBtn, {
data <- dplyr::filter(df(), cyl != input$selected_CarCylinders)
# Update `selectInput` to filter out the choices too (for good measure)
updateSelectInput(session, "selected_CarCylinders", choices = data$cyl)
# Update the `reactiveVal` value
df(data)
})
}