R Shiny: Reset selectizeInput selection upon actionButton input - r

Question

I am trying to reset selectizeInput selections upon actionButton input.
Please see the following code, in which I cannot get the eventReactive to function:
library(shiny)
ui <- fluidPage(
column(width = 4,algin = "center", uiOutput("choose_Number")) ,
br(),
column(width = 4, algin = "center",div(
align = "center", actionButton('delete','Delete Number(s)',style="color: #fff; background-color: #53C1BE")))
)
server <- function(input, output, session) {
output$choose_Number <- renderUI({
selectizeInput("choose_Number", "Select Number", as.list(c(1,2,3,4)),selected = c(''), options=list(create=TRUE,'plugins' = list('remove_button'),
persist = FALSE), multiple = TRUE)
})
##### I am trying to reset the selectizeInput upon input from the Delete button
eventReactive(input$delete, {updateSelectizeInput("choose_Number", "Select Number", as.list(c(1,2,3,4)), selected = c(''),options=list(create=TRUE,'plugins' = list('remove_button'),
persist = FALSE), multiple = TRUE)} )
}
shinyApp(ui, server)
Thank you.

Answer 1

The biggest issue was that the session was missing. You can omit the session argument if you want to but then you need to name all other arguments because session is the first in line. Second issue was that you can set multiple in selectizeInput but not later when using updateSelectizeInput() to change it.
Minor improvements: the manual recommends using character() to deselect the current choice. As mentioned by #YBS you do not provide a reactive value so that observeEvent is the better choice here.
PS: are you sure you want to centre align the columns? It looks strange.
library(shiny)
ui <- fluidPage(
column(width = 4, align = "center", uiOutput("choose_Number")),
br(),
column(width = 4, align = "center", div(
align = "center",
actionButton('delete', 'Delete Number(s)', style="color: #fff; background-color: #53C1BE"))
)
)
server <- function(input, output, session) {
output$choose_Number <- renderUI({
selectizeInput("choose_Number", "Select Number", as.list(c(1,2,3,4)), selected = character(),
options = list(create=TRUE,'plugins' = list('remove_button'), persist = FALSE),
multiple = TRUE)
})
##### I am trying to reset the selectizeInput upon input from the Delete button
observeEvent(input$delete, {
updateSelectizeInput(session, "choose_Number", choices = as.list(1:4),
selected = character(0),
options = list(create=TRUE, 'plugins' = list('remove_button'), persist = FALSE))
})
}
shinyApp(ui, server)