api.R

# Dean Attali, July 2015

# listen for when javascript makes an api call
observeEvent(session$input[['api']], {
  # grab all the call parameters
  params <- session$input[['api']]
  
  # determine what R method to call
  method <- params[['_method']]
  method <- sprintf("api.%s", method)
  
  # save the request ID
  reqid  <- params[['_reqid']]
  
  # remove the meta params from the param list
  params[['_method']] <- NULL
  params[['_reqid']]  <- NULL
  
  # attempt to run the R function and return the response, along with request ID
  tryCatch({
    response <- do.call(method, as.list(list(params)))
    response <- as.list(response)
    response['_reqid'] <- reqid
    
    session$sendCustomMessage(type = "api.callback", response);
  },
  # if an error occurs, call the error callback
  error = function(err) {
    response <- list(message = err$message,
                     `_reqid`  = reqid)
    session$sendCustomMessage(type = "api.failureCallback", response);
  })
})