Question

我尝试使用ReactivePoll来更新数据框。当a）将新行添加到数据库表并且b）input$type更改时，check函数应返回不同的值。

# checks to see if input$type has changed or the table corresponding to input$type has grown
check.data <- function() {
    row.count <- 0
    if (data.connection$source == "pg") {
        pg.connection$connection <- dbConnect(pg.connection$driver, dbname = pg.settings.database(), host = pg.settings.host(), port = as.integer(pg.settings.port()), user = pg.settings.user(), password = pg.settings.password())
        row.count <- as.integer(dbGetQuery(pg.connection$connection, paste0("SELECT count(*) FROM ", input$type ,"datum")))
        dbDisconnect(pg.connection$connection)
    }
    print(row.count)    # make sure return value is changing when it should
    row.count
}
# refreshes data
refresh.data <- function() {
    print("check")      # check if function is executing
    frame <- data.frame()
    if (data.connection$source == "pg") {
        pg.connection$connection <- dbConnect(pg.connection$driver, dbname = pg.settings.database(), host = pg.settings.host(), port = as.integer(pg.settings.port()), user = pg.settings.user(), password = pg.settings.password())
        frame <- dbReadTable(pg.connection$connection, paste0(input$type, "datum"))
        dbDisconnect(pg.connection$connection)
    }
    frame
}
data <- reactivePoll(15000, NULL, check.data, refresh.data)

根据R Shiny的文档，＆＃34;检查功能通过返回与上次呼叫时不同的值来指示更改。＆＃34;我已经确认row.count正在发生变化，但是＆＃34;检查＆＃34;从不打印，暗示值函数永远不会执行。我知道行计数不是检查更改的可靠方法（表可能具有相同的行数），但row.count 正在更改。

R闪亮检查功能不触发值功能

0 个答案: