Load global var before using it in UI

shiny

#1

Hello everyone,

I'm new into the R community and pleased to be part of it.

Unfortinately, I'm actually stuck on a little problem: I'm unable to load the value of a global var before it is used in the UI. Here is my code:

# global.R
globalVar = 0


# ui.R
library(shiny)
library(RMySQL)

db = dbConnect(dbDriver("MySQL"),
        dbname = "db_name",
        host = "127.0.0.1",
        port = 3306,
        user = "db_user",
        password = "db_password")

# Returns 1 in our case.
getSomething = function() {
    dbGetQuery(db, sprintf("SELECT column FROM Table WHERE Id = %s", globalVar));
}

gender <- getSomething() # = 1

shinyUI(fluidPage(theme = "style.css",
	titlePanel(title="", windowTitle="Test"),

	wellPanel(
		h4("Test"), br(),

		selectInput("gender","Gender",choices = c("Male" = 1, "Female" = 2), selected=gender)
	)
 ))


# server.R
library(urltools)

shinyServer(function(input, output, session) {
	observe({url <- sprintf(
		"%s//%s:%s%s%s",
		session$clientData$url_protocol,
		session$clientData$url_hostname,
		session$clientData$url_port,
		session$clientData$url_pathname,
		session$clientData$url_search)
	
		urlParams <- param_get(urls = url, parameter_names = c("id")))

		globalVar <<- paramsUrl$id
	})
})

So if I load the app for the first time, globalVar = 0 for the UI but R Studio tells me that it is equal to the value passed in the id url param.

Do you think it is possible to do what I want to do?

Thank you very much for your help!


#2

I have been misunderstooding the concept... I got it working this way:

# ui.R
library(shiny)

shinyUI(fluidPage(theme = "style.css",
	titlePanel(title="", windowTitle="Test"),

	wellPanel(
		h4("Test"), br(),

		selectInput("gender","Gender",choices = c("Male" = 1, "Female" = 2), selected=1)
	)
))

# server.R
library(shiny)
library(urltools)
library(RMySQL)

db = dbConnect(dbDriver("MySQL"),
        dbname = "db_name",
        host = "127.0.0.1",
        port = 3306,
        user = "db_user",
        password = "db_password")

# Returns 2 in this case.
getSomething = function(id) {
    dbGetQuery(db, sprintf("SELECT column FROM Table WHERE Id = %s", id));
}

shinyServer(function(input, output, session) {
	observe({url <- sprintf(
		"%s//%s:%s%s%s",
		session$clientData$url_protocol,
		session$clientData$url_hostname,
		session$clientData$url_port,
		session$clientData$url_pathname,
		session$clientData$url_search)
	
		urlParams <- param_get(urls = url, parameter_names = c("id")))

		gender <- getSomething(urlParams$id) # = 2
		
		updateSelectInput(session, "gender",
			selected = gender
		)
	})
})

Sorry for the stupid question...