根据shiny R中的另一个selectInput值更改默认值

library(shiny)

ui <- fluidPage(
  selectInput("defaultInput", "选择默认值", choices = c("选项1", "选项2", "选项3")),
  selectInput("triggerInput", "触发事件", choices = c("选项A", "选项B", "选项C")),
  textOutput("output")
)

server <- function(input, output, session) {
  observeEvent(input$triggerInput, {
    if (input$triggerInput == "选项A") {
      updateSelectInput(session, "defaultInput", selected = "选项1")
    } else if (input$triggerInput == "选项B") {
      updateSelectInput(session, "defaultInput", selected = "选项2")
    } else if (input$triggerInput == "选项C") {
      updateSelectInput(session, "defaultInput", selected = "选项3")
    }
  })
  
  output$output <- renderText({
    paste("默认值为:", input$defaultInput)
  })
}

shinyApp(ui, server)