CODEWITHSUNDEEP
rscopeshinyglobalshiny-reactivity
S.V. Den Boer
S.V. Den Boer

Reputation: 59

Shiny: observe change in global variable

I am making a very simple game in Shiny. Basically every player plays in their own session, but they share 1 global variable to keep track of the scores of each player.

I think I'm succeeding having sessions update the global 'scores' variable, but for some (probably dumb) reason I cannot get the global variable to act as a reactive value (i.e. automatically triggering updateActionButton). Minimal code below:

working example:

score <- c(100) 

ui <- fluidPage(
  titlePanel("Hello Shiny!"),
  mainPanel(
    actionButton("increase_score", label = " increase score player 1 "),
    verbatimTextOutput("show_score_p1")
  )
)

# Server logic
server <- function(input, output){
  observeEvent(input$increase_score,{
    score[1] <- score[1]+10
  })
  output$show_score_p1 <- renderText({paste(score[1])})  
}

shinyApp(ui,server)

I tried a couple of methods to try and make my global 'score' to be reactive, i.e. makeReactiveBinding(score), but to no avail. Any ideas? Definitely feels like I'm missing something super-obvious

Upvotes: 3

Views: 3588

Answers (1)

Jim Chen
Jim Chen

Reputation: 3729

Use can use a helpful function called reactiveValues

library(shiny)
ui <- fluidPage(
  titlePanel("Hello Shiny!"),
  mainPanel(
    actionButton("increase_score", label = " increase score player 1 "),
    verbatimTextOutput("show_score_p1")
  )
)

score<-reactiveValues(a=100)
# Server logic
server <- function(input, output){

  observeEvent(input$increase_score,{
    score$a <- score$a+10
  })
  output$show_score_p1 <- renderText({
    score$a
  })  
}

shinyApp(ui,server)

Upvotes: 2

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