Shiny应用reactive picker input首次访问未按默认时段更新选项求解

问题出在observeEvent的ignoreInit参数配置上：你设置了ignoreInit = TRUE，会让Shiny在应用初始化阶段跳过该观察者的执行，因此首次加载时不会根据默认选中的period1更新国家选择器的禁用状态，导致全部国家都可选。

只需将ignoreInit = TRUE修改为ignoreInit = FALSE，或者直接删除该参数（observeEvent默认该参数值为FALSE），即可让初始化阶段自动执行更新逻辑，首次加载就仅显示对应时段的可选国家。

修正后的完整代码如下：

library(shiny)
library(shinyWidgets)

choice_name <- c('UK','USA','BE','BE')
choice_id <- c(1, 2, 3,3)
period <- c('period1', 'period1', 'period3', 'period3')
data <- data.frame(choice_name, choice_id, period)

choices_picker <- unique(data$choice_id)
names(choices_picker) <- unique(data$choice_name)


ui <- bootstrapPage(                
  absolutePanel(left = 10, bottom = 10, draggable = TRUE, 
  selectInput(inputId = "input_period", label = "Period",
    choices = c("Period 1: X to Z" = "period1", "Period 2: X to Y" = "period2", "Period 3: X to X" = "period3"),
    selected = "period1"),
  pickerInput(inputId = "picker_cty",
    label = "Select Country",
    choices = choices_picker,
    multiple = TRUE),
))

server <- function(input, output, session) {
  
  # Reactive pickerInput ---------------------------------
  observeEvent(input$input_period, {
    
    data1 <- data[data$period == input$input_period,]
    datau <- unique(data$choice_id)
    data1u <- unique(data1$choice_id)
    
    disabled_choices <- ifelse(datau %in% data1u, 0,1)
    
    # Generate reactive picker input
    updatePickerInput(session = session, 
                      inputId = "picker_cty",
                      choices = choices_picker,
                      choicesOpt = list(
                        disabled = disabled_choices,
                        style = ifelse(disabled_choices,
                                       yes = "color: rgba(119, 119, 119, 0.5);",
                                       no = "")
                      ))
  }) # 移除了ignoreInit = TRUE参数
  
}

shinyApp(ui, server)

注：当前示例数据集没有period2对应的国家记录，因此选中period2时所有国家都会被禁用，属于预期行为。

内容的提问来源于stack exchange，提问作者AnEostig