在Shiny应用程序中构建被动查询构建并导出结果

Question

我有一个Shiny应用程序，它查询本地数据库并在表中返回结果。有两个查询可以运行，每个查询都由一个单独的操作按钮控制。

该应用程序工作正常，但我尝试制作数据下载按钮时遇到了问题。问题是，我已经做出了两个单独的反应函数来获取每个查询，并且我无法弄清楚如何使两个查询的结果都是相同的'对象'[赦免可能不正确的术语]，以便相同的数据 - 下载按钮将根据运行的查询下载当前数据。一个丑陋的解决方案是只做两个下载按钮，但我确定有一个优雅的解决方案。

这里是我的代码：

global.R：

library(shiny) 
library(RSQLite) 
library(data.table) 
library(dplyr) 
library(zoo) 
library(igraph) 

# Import parts list and materials list 
setwd("REDACTED/Scripts/shiny/LegislationQuery/") 
partList <- read.csv("partList.csv") 
materialsList <- read.csv("materialsList.csv") 

# Set up local.db 
if(file.exists("local.db")) file.remove("local.db") 
myDB<-dbConnect(SQLite(),"local.db") 
dbWriteTable(myDB, "partList", partList, overwrite = TRUE) 
dbWriteTable(myDB, "Materials", materialsList, overwrite = TRUE) 

server.R：

library(shiny) 
library(RSQLite) 
library(data.table) 
library(dplyr) 
library(zoo) 
library(igraph) 

shinyServer(function(input, output) { 

sqlDown <- reactive ({paste("with recursive Parts(P,S, Level) as (select Part as P, SubPart as S, 0 from partList union select Parts.P, partList.SubPart as S, Parts.Level + 1 as Level from Parts, partList where Parts.S = partList.Part) select P as Part, S as SubPart, Level from Parts where P = ","'", input$partForQuery, "'", sep = "")}) 
sqlUp <- reactive ({paste("with Parts(subPart, part, level) as (select SubPart as subPart, Part as part, 0 as level from partList where subPart =", "'", input$partForQuery, "'", "union select partList.SubPart, partList.Part as part, Parts.level - 1 as level from Parts, partList where Parts.part = partList.SubPart) select subPart as SubPart, part as Part, level as Level from Parts", sep = "")}) 

    queryDownData <- function() {dbGetQuery(myDB, sqlDown())} 
    queryUpData <- function() {dbGetQuery(myDB, sqlUp())} 

    observeEvent(input$RunDownQuery, { 
    output$table <- renderDataTable(data.table({ 
    data = queryDownData()})) 
    }) 
    observeEvent(input$RunUpQuery, { 
    output$table <- renderDataTable(data.table({ 
    data = queryUpData()})) 
    }) 

    output$downloadData <- downloadHandler(
    filename = function() { paste(input$partForQuery, '.csv', sep='') }, 
    content = function(file) { 
     write.csv(queryDownData(), file) 
    } 
) 
}) 

ui.R：

library(shiny) 
library(data.table) 

shinyUI(pageWithSidebar(

    headerPanel("Part Query"), 

    sidebarPanel(
    textInput("partForQuery", "Part Number:"), 

    fluidRow(
    actionButton("RunDownQuery", label = "Run Query (Down)"), 
    actionButton("RunUpQuery", label = "Run Query (Up)") 
    ), 
    downloadButton('downloadData', 'Download') 
), 

    mainPanel(
    dataTableOutput("table") 
) 
)) 

Answer 1

像这样的东西应该工作：

library(shiny) 
library(RSQLite) 
library(data.table) 
library(dplyr) 
library(zoo) 
library(igraph) 

shinyServer(function(input, output) { 

    whichQuery <- c() 

    sqlDown <- reactive ({paste("with recursive Parts(P,S, Level) as (select Part as P, SubPart as S, 0 from partList union select Parts.P, partList.SubPart as S, Parts.Level + 1 as Level from Parts, partList where Parts.S = partList.Part) select P as Part, S as SubPart, Level from Parts where P = ","'", input$partForQuery, "'", sep = "")}) 
    sqlUp <- reactive ({paste("with Parts(subPart, part, level) as (select SubPart as subPart, Part as part, 0 as level from partList where subPart =", "'", input$partForQuery, "'", "union select partList.SubPart, partList.Part as part, Parts.level - 1 as level from Parts, partList where Parts.part = partList.SubPart) select subPart as SubPart, part as Part, level as Level from Parts", sep = "")}) 

    queryDownData <- function() {dbGetQuery(myDB, sqlDown())} 
    queryUpData <- function() {dbGetQuery(myDB, sqlUp())} 

    observeEvent(input$RunDownQuery, { 
    whichQuery <<- "Down" 
    output$table <- renderDataTable(data.table({ 
     data = queryDownData()})) 
    }) 
    observeEvent(input$RunUpQuery, { 
    whichQuery <<- "Up" 
    output$table <- renderDataTable(data.table({ 
     data = queryUpData()})) 
    }) 

    output$downloadData <- downloadHandler(
    filename = function() { paste(input$partForQuery, '.csv', sep='') }, 
    content = function(file) { 
     write.csv(ifelse(whichQuery=="Down",queryDownData(),queryUpData()), file) 
    } 
) 
}) 

whichQuery持有最后按下哪个按钮，然后确定要下载的文件时使用该值。