I have a rather complex Shiny application and something weird happens: When I print out some of my intermediate steps the App makes, everything gets printed out twice. That means, everything gets evaluated etc. twice.
I know without seeing the progamme its rather hard to tell what causes the problem, but maybe someone can pin point me (based on experierence/knowledge) what might be the problem.
Like I mentioned in the comment, isolate() should solve your problem. Beyond the documentation of Rstudio http://shiny.rstudio.com/articles/reactivity-overview.html I recommend the following blog article for interesting informations beyond the RStudio docu. https://shinydata.wordpress.com/2015/02/02/a-few-things-i-learned-about-shiny-and-reactive-programming/
In a nutshell, the easiest way to deal with triggering is to wrap your code in isolate() and then just write down the variables/inputs, that should trigger changes before the isolate.
output$text <- renderText({
input$mytext # I trigger changes
isolate({ # No more dependencies from here on
# do stuff with input$mytext
# .....
finishedtext = input$mytext
return(finishedtext)
})
})
Reproducible example:
library(shiny)
ui <- fluidPage(
textInput(inputId = "mytext", label = "I trigger changes", value = "Init"),
textInput(inputId = "mytext2", label = "I DONT trigger changes"),
textOutput("text")
)
server <- function(input, output, session) {
output$text <- renderText({
input$mytext # I trigger changes
isolate({ # No more dependencies from here on
input$mytext2
# do stuff with input$mytext
# .....
finishedtext = input$mytext
return(finishedtext)
})
})
}
shinyApp(ui, server)
I encountered the same problem when using brush events in plotOutput. The solution turned out to be resetOnNew = T when calling plotOutput to prevent changes in my plot causing the brush event to be evaluated again.
