feat: remove_rules method

[mnaegelin]

I had the issue of dynamically generated textInputs, where the user can click on a button to create resp. delete input fields. If the field exists, it is required, but if it is deleted I wanted to remove also the corresponding rules - otherwise the validator would always stay FALSE. Thus I added the method remove_rules(inputId) which simply removes all rules with the corresponding inputId from the validator, and re-enables it if necessary to update the displayed feedback.

Not sure the added method extrapolates well across all scenarios, but it worked for my use case and I think this might also be useful for issue #77 and potentially #71, so I thought I'd share.

example use case:

library(shiny)
library(shinyjs)
library(shinyvalidate)

ui <- fluidPage(
  shinyjs::useShinyjs(),
  
  textInput('author_1', "Author 1", "", placeholder = "Last name, first name"),
  uiOutput("additional_authors"),
  actionButton("add_author_btn", "Add author"),
  actionButton("del_author_btn", "Delete author", class = "btn btn-danger"),
  p('Check if the validation rules are passed:'),
  verbatimTextOutput('check_iv')
)

server <- function(input, output, session) {
  iv <- InputValidator$new()
  iv$add_rule("author_1", sv_required())
  iv$enable()
  
  # Keep track of the number of authors
  author_count <- reactiveVal(1)
  
  # Enable delete button only if there are more than 1 authors
  observe({
    shinyjs::toggleState(id = "del_author_btn", condition = author_count() > 1)
  })
  
  # Add author input if add button is clicked
  observeEvent(input$add_author_btn, {
    author_count(author_count() + 1)
    author_id <- paste0('author', author_count())
    insertUI(
      selector = "#additional_authors",
      where = "beforeBegin",
      ui = div(id = author_id,
               textInput(author_id,
                     paste0("Author ", author_count()), 
                     "", placeholder = "Last name, first name"))
    )
    # add validation rule
    iv$add_rule(author_id, sv_required())
  })
  
  # Delete author input if delete button is clicked 
  observeEvent(input$del_author_btn, {
    author_id <- paste0('author', author_count())
    removeUI(selector = paste0("#", author_id))
    # remove the corresponding author rules
    iv$remove_rules(author_id)
    author_count(author_count() - 1)
  })
  
  # Check the output of iv$is_valid()
  output$check_iv <- renderPrint({
    iv$is_valid()
  })
}

shinyApp(ui, server)

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