我想在 Shiny 中创建一个reactiveValues
对象,其内容定义为输入小部件中包含的值。我设法做到了,但我的实现似乎不必要地笨拙:
- 创建空
reactiveValues
对象 - 监控输入微件的值何时随
observeEvent
变化 - 使用输入小部件中的非反应值为
reactiveValues
对象分配值 (isolate
(
下面是一个示例:
ui <- fluidPage(
fluidRow(
column(2, radioButtons("main", label = "Main dish", choices = list("salad", "pasta"))),
column(2, radioButtons("desert", label = "Desert", choices = list("fruit", "cake"))),
column(8, actionButton("extra", "Louder!", style="background-color: #ffdb99"))
),
verbatimTextOutput("myorder")
)
server <- function(input, output, session) {
# 1. Create reactiveValues object
menuR <- reactiveValues()
# 2. Update values whenever widgets change
observeEvent(c(input$main, input$desert),
menuR[["meal"]] <- paste(c(isolate(input$main), isolate(input$desert)), collapse = " & ")
)
# 3. Perform operations on object values
observeEvent(input$extra,
menuR[["meal"]] <- paste0(toupper(menuR[["meal"]]), "!!!")
)
output$myorder <- renderText(menuR[["meal"]])
}
shinyApp(ui, server)
我非常想像这样直接创建reactiveValues
对象(大大简化了上面的代码(:
# Set values upon creation
menuR <- reactiveValues(meal = paste(c(input$main, input$desert), collapse = " & "))
这是行不通的input$main
因为它是反应性的......
我本以为使用从小部件获得的值定义reactiveValues
对象将是一件很常见的事情。
我错过了什么吗?
感谢您的帮助,
雨 果
您可以使用reactive()
而不是reactiveValues()
来执行此操作。menuR
是一个响应对象,它依赖于main
和desert
的输入值。定义服务器代码后,可以通过调用服务器代码中的menu()
来使用它。此外,这使您无需使用isolate()
,因为您可以将menu
的值设置为observeEvent()
中的响应对象。
library(shiny)
ui <- fluidPage(
fluidRow(
column(2, radioButtons("main", label = "Main dish", choices = list("salad", "pasta"))),
column(2, radioButtons("desert", label = "Desert", choices = list("fruit", "cake"))),
column(8, actionButton("extra", "Louder!", style="background-color: #ffdb99"))
),
verbatimTextOutput("myorder")
)
server <- function(input, output, session) {
menuR <- reactive({
paste(c(input$main, input$desert), collapse = " & ")
})
observeEvent(
input$extra,
menuR <- reactive({
toupper(paste(c(input$main, input$desert), collapse = " & "))
})
)
output$myorder <- renderText(menuR())
}
shinyApp(ui, server)
编辑
我之前误解了这个问题。您可以使用eventReactive()
来监视输入并在用户输入更改时进行更改。我还为用户尚未单击操作按钮添加了一个默认值。
library(shiny)
ui <- fluidPage(
fluidRow(
column(2, radioButtons("main", label = "Main dish", choices = list("salad", "pasta"))),
column(2, radioButtons("desert", label = "Desert", choices = list("fruit", "cake"))),
column(8, actionButton("extra", "Louder!", style="background-color: #ffdb99"))
),
verbatimTextOutput("myorder")
)
server <- function(input, output, session) {
# Set a 'default' value for the output
default.menuR <- reactive({
paste(c(input$main, input$desert), collapse = " & ")
})
menuR <- eventReactive(input$extra, {
toupper(paste(c(input$main, input$desert), collapse = " & "))
})
# Initial state of the button is 0, which displays 'default' value
output$myorder <- renderText({
if (input$extra == 0) {
return(default.menuR())
}
menuR()
})
}
shinyApp(ui, server)
希望这有帮助!
我采纳了 Vishesh 的建议并使其发挥作用。它看起来与我的原始示例没有太大区别,并且仍然需要重复几行代码。 它的工作原理是每次其中一个小部件更改时覆盖反应对象。
library(shiny)
ui <- fluidPage(
fluidRow(
column(2, radioButtons("main", label = "Main dish", choices = list("salad", "pasta"))),
column(2, radioButtons("dessert", label = "dessert", choices = list("fruit", "cake"))),
column(8, actionButton("extra", "Louder!", style="background-color: #ffdb99"))
),
verbatimTextOutput("myorder")
)
server <- function(input, output, session) {
menuR <- reactive({
paste(c(input$main, input$dessert), collapse = " & ")
})
# Render text when app loads
output$myorder <- renderText(menuR())
# Update reactive object and re-render text (button 'extra')
observeEvent(
input$extra,{
temp <- toupper(paste(c(input$main, input$dessert), collapse = " & "))
menuR <<- reactive(temp)
output$myorder <- renderText(menuR())
}
)
# Update reactive object and re-render text (button 'main' or 'dessert')
observeEvent(c(input$main, input$dessert),{
menuR <- reactive(paste(c(input$main, input$dessert), collapse = " & "))
output$myorder <- renderText(menuR())
})
}
shinyApp(ui, server)