leafletProxy.Rd

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/utils.R
\name{leafletProxy}
\alias{leafletProxy}
\title{Send commands to a Leaflet instance in a Shiny app}
\usage{
leafletProxy(
  mapId,
  session = shiny::getDefaultReactiveDomain(),
  data = NULL,
  deferUntilFlush = TRUE
)
}
\arguments{
\item{mapId}{single-element character vector indicating the output ID of the
map to modify (if invoked from a Shiny module, the namespace will be added
automatically)}

\item{session}{the Shiny session object to which the map belongs; usually the
default value will suffice}

\item{data}{a data object; see Details under the \code{\link[=leaflet]{leaflet()}} help
topic}

\item{deferUntilFlush}{indicates whether actions performed against this
instance should be carried out right away, or whether they should be held
until after the next time all of the outputs are updated; defaults to
\code{TRUE}}
}
\description{
Creates a map-like object that can be used to customize and control a map
that has already been rendered. For use in Shiny apps and Shiny docs only.
}
\details{
Normally, you create a Leaflet map using \code{\link[=leaflet]{leaflet()}}.
This creates an in-memory representation of a map that you can customize
using functions like \code{\link[=addPolygons]{addPolygons()}} and \code{\link[=setView]{setView()}}.
Such a map can be printed at the R console, included in an R Markdown
document, or rendered as a Shiny output.

In the case of Shiny, you may want to further customize a map, even after it
is rendered to an output. At this point, the in-memory representation of the
map is long gone, and the user's web browser has already realized the Leaflet
map instance.

This is where \code{leafletProxy()} comes in. It returns an object that can
stand in for the usual Leaflet map object. The usual map functions like
\code{\link[=addPolygons]{addPolygons()}} and \code{\link[=setView]{setView()}} can be called, and
instead of customizing an in-memory representation, these commands will
execute on the live Leaflet map instance.
}
\examples{
library(shiny)

ui <- fluidPage(
  leafletOutput("map1")
)

map <- leaflet() \%>\% addCircleMarkers(
  lng = runif(10),
  lat = runif(10),
  layerId = paste0("marker", 1:10))
server <- function(input, output, session) {
  output$map1 <- renderLeaflet(map)

  observeEvent(input$map1_marker_click, {
    leafletProxy("map1", session) \%>\%
      removeMarker(input$map1_marker_click$id)
  })
}

app <- shinyApp(ui, server)
\donttest{if (interactive()) app}

}