r - 如何重置 react 值？

Question

重置单个 react 值只需通过 reactiveVal(NULL) 即可完成。但是，如何才能完全重置 reactiveValues()？

虚拟应用程序包含我的一些方法来保留新鲜和干净的 react 值，但它们都没有真正做到我希望它们做的事情。此外，在观察 reactiveValues 时似乎有一种奇怪的行为。除非单击 Trigger 按钮，否则它们不会在清洁后触发 react 。当我检查他们的状态时，他们看起来很好。

library(shiny)
library(magrittr)

# UI ---------------------------------------------------------------------------
ui <- fluidPage(
    actionButton("create", "Create"),
    actionButton("reset", "Reset"),
    actionButton("trigger", "Trigger"),
    textOutput("out")
)

# Server -----------------------------------------------------------------------
server <- function(input, output, session) {

    vals <- reactiveValues()
    ids <- reactiveVal()
    display <- reactiveVal()

    # insert letter when clicked
    observeEvent(input$create, {
        id <- as.character(length(ids()))
        vals[[id]] <- sample(LETTERS, 1)
        ids(c(ids(), id))
    })

    observeEvent(input$reset, {
        # Options to reset reactive Values -------------------------------------
        vals <<- reactiveValues()
        # vals <- NULL
        for(i in names(vals)) vals[[i]] <- NULL # deletes content but not the names

        # resetting reactiveVal() is easily done via NULL
        ids(NULL)
        display(NULL)
    })

    observe({
        if(input$trigger) browser()
        text <- reactiveValuesToList(vals) %>% paste(collapse = ", ")
        display(text)
    })

    output$out <- renderText(display())
}

shinyApp(ui, server)

P.S.:该示例并未完全精简，因为我希望它反射(reflect)我的实际 react 链。

Answer 1

显然你不能完全取消 reactiveValues

看看:

Shiny: How to initialize empty reactiveValues with an actionButton?

shiny: How to update a reactiveValues object?

根据这两个问题的答案，作为一种解决方法，可以将值保存在 reactiveValues 对象的列表中，您的代码将如下所示:

library(shiny)
library(magrittr)

# UI ---------------------------------------------------------------------------
ui <- fluidPage(
  actionButton("create", "Create"),
  actionButton("reset", "Reset"),
  actionButton("trigger", "Trigger"),
  textOutput("out")
)

# Server -----------------------------------------------------------------------
server <- function(input, output, session) {
  # initialize vals with a list
  vals <- reactiveValues('foo' = list())
  ids <- reactiveVal()
  display <- reactiveVal()

  observeEvent(input$create, {
    id <- as.character(length(ids()))
    # add values to the list
    vals$foo[[id]] <- sample(LETTERS, 1)
    ids(c(ids(), id))
  })

  observeEvent(input$reset, {
    # reset the list
    vals$foo <- NULL
    ids(NULL)
  })

  observe({
    # if(input$trigger) browser()
    text <- reactiveValuesToList(vals) %>% paste(collapse = ", ")
    display(text)
  })

  output$out <- renderText({
    text <- vals$foo %>% paste(collapse = ", ")
    display(text)
    display()
  })
}

shinyApp(ui, server)