R:renderUI内函数中的可选参数不起作用

在我的应用程序中，我使用renderUI仅在选择数据帧后显示过滤器。我编写了自己的函数，将selectInput元素分配到函数参数给定的许多列中

我添加了指定

rosterWidth

、每行应显示的列数和

columnWidth

、传递给

shinny:：column

的参数作为宽度参数的可能性

理想情况下，我只需要指定其中一个参数，我的函数应该根据

otherParam=12%/%firstParam

（因为12是允许的最大宽度）计算另一个参数

我的职能：

arrangeHtmlItems <- function(rosterWidth, columnWidth, htmlItemList, actionButton) {
  if (missing(rosterWidth) && missing(columnWidth)) {
    stop("Specify either rosterWidth or columnWidth")
    return(NULL)
  }

  if (missing(rosterWidth)) {
    rosterWidth <- 12 %/% columnWidth
  }

  if (missing(columnWidth)) {
    columnWidth <- 12 %/% rosterWidth
  }

  # number of columns needed
  numCols <- min(length(htmlItemList), rosterWidth)

  # item indices to use in for-loop
  itemIndices <- 1:length(htmlItemList)

  # column indices: column 1 should be first, column 0 should be the last column,
  # since i %% numCols for i == numCols is 0
  # (in a four-column roster, the first item is attributed to column 0 since 4 %% 4 is 0)
  columnIndices <- c(1:(numCols - 1), 0)

  cols <- list()
  for (i in 1:length(columnIndices)) {
    curIndex <- columnIndices[i]
    curCol <- htmlItemList[which(itemIndices %% numCols == curIndex)]
    cols[[i]] <- column(columnWidth, curCol)
  }

  # return action button in fluid row if given as parameter
  if(missing(actionButton)) {
    return(fluidRow(cols))
  } else {
    return(fluidRow(cols, actionButton))
  }
}

---

为什么会这样？如何在

renderUI（）中的函数中正确使用可选函数参数？
您的代码是正确的。。。除了actionButton的最后一个参数未命名外。您需要执行
排列Htmlitems（罗斯特宽度=…，htmlItemList=…，actionButton=…）
，否则actionButton将作为列宽度传入。我通过在函数中设置断点发现了这一点，你也可以这样做。你说得对！非常感谢你！从现在起，我将使用断点。
library(shiny)
library(dplyr)
library(stringr)
library(magrittr)
library(ggplot2)

source("functions.R")

server <- function(input, output) {
  CtryData <- eventReactive(input$goButton, {
    data <- data.frame(mpg)
  })

  output$colFilter <- renderUI({
    # make objects out of reactive objects
    data <- CtryData()
    cols <- colnames(data)

    # function returns fluidRows with number of columns specified by rosterWidth
    # dynamically adjusts the number of items per column based on number of filters produced in the lapply-function
    arrangeHtmlItems(
      # !!! 
      # rosterWidth * columnWidth must be <= 12
      # !!!
      rosterWidth = 2
      , columnWidth = 6
      , htmlItemList = lapply(cols, function(i) {
        vec_choices <- c("(All)", paste0(sort(unique(data[ ,i])))) # paste0 is needed since otherwise level numbers, not levels are listed for factors 
        selectInput(
          inputId = paste0("colFilter_", i),
          paste0("Select ", i),
          choices = vec_choices,
          multiple = TRUE,
          selectize = FALSE,
          size = 6,
          selected = "(All)"
        )
      })
      , actionButton("colFilterButton", "Go")
    )
  })
}

ui <- fluidPage(
  fluidRow(
    actionButton("goButton", "Go")
    , uiOutput("colFilter")
  )
)

shinyApp(ui = ui, server = server)

arrangeHtmlItems <- function(rosterWidth = NULL, columnWidth = NULL, htmlItemList, actionButton) {
  ...
  if (is.null(columnWidth)) {
    ...
  }
  ...
}