Shiny - RStudio：conditionalPanel 在條件為.Platform$OS.type 時不起作用

Question

Shiny 顯示所有內容，即使條件不滿足，例如.Platform$OS.type == 'windowsxxx'。 由於我使用 window，所以 command.Platform$OS.type 將返回“windows”，而 condition.Platform$OS.type == 'windowsxxx' 應該為 FALSE，但 shiny 似乎沒有評估此條件並顯示其中的所有內容條件面板。 示例代碼如下，每一個建議都非常感謝

    library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30),
            
            conditionalPanel(
              condition = ".Platform$OS.type == 'windowsxxx'",
              sliderInput("breakCount", "This is a conditional sliderInput", min=1, max=1000, value=10)
            )
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("distPlot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

}

# Run the application 
shinyApp(ui = ui, server = server)

Answer 1

如果您將.Platform$OS.type作為字符串傳遞給conditionalPanel的condition參數，它需要一個 JavaScript 表達式 - 它不會被 R 執行。 請檢查以下內容：

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(
  
  # Application title
  titlePanel("Old Faithful Geyser Data"),
  
  # Sidebar with a slider input for number of bins 
  sidebarLayout(
    sidebarPanel(
      sliderInput("bins",
                  "Number of bins:",
                  min = 1,
                  max = 50,
                  value = 30),
      
      conditionalPanel(
        condition = sprintf("'%s' == 'windowsxxx'", .Platform$OS.type),
        sliderInput("breakCount", "This is a conditional sliderInput", min=1, max=1000, value=10)
      )
    ),
    
    # Show a plot of the generated distribution
    mainPanel(
      plotOutput("distPlot")
    )
  )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
  
}

# Run the application 
shinyApp(ui = ui, server = server)