为选定的输入选项获取数据帧的唯一值,但仅当在server.ui中定义了数据帧而不是全局

闪亮应用示例:

library(tidyverse)
library(shiny)


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

   # Application title
   titlePanel("example"),

   # Sidebar with a slider input for number of bins 
   sidebarLayout(
      sidebarPanel(
         sliderInput("bins",
                     "Number of bins:",
                     min = 1,
                     max = 50,
                     value = 30),

      selectInput(inputId = "cut",
                  label = "cut",
                  # choices =  unique(diamonds$cut), # works
                  choices =  unique(my_diamonds$cut), # does not work
                  selected = "Ideal")

      ),

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

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

  my_diamonds <- diamonds

   output$distPlot <- renderPlot({
      # generate bins based on input$bins from ui.R
      x    <- my_diamonds$carat
      bins <- seq(min(x), max(x), length.out = input$bins + 1)

      # draw the histogram with the specified number of bins
      hist(x, breaks = bins, col = 'darkgray', border = 'white')
   })
}

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

在这种情况下,我使用的是一个人造数据框“我的钻石”。在我的实际代码中,我使用dbplyr连接到一个数据库,然后对它进行一些转换,因此在ui部分复制它似乎是浪费。

在本例中,使用服务器部分中定义的数据帧获取唯一值的“正确”方法是什么 my_diamonds$cut 要用作选定输入的下拉选择吗?