在Shiny應用程序中構建被動查詢構建並導出結果

Question

我有一個Shiny應用程序，它查詢本地數據庫並在表中返回結果。有兩個查詢可以運行，每個查詢都由一個單獨的操作按鈕控制。

該應用程序工作正常，但我嘗試製作數據下載按鈕時遇到了問題。問題是，我已經做出了兩個單獨的反應函數來獲取每個查詢，並且我無法弄清楚如何使兩個查詢的結果都是相同的'對象'[赦免可能不正確的術語]，以便相同的數據 - 下載按鈕將根據運行的查詢下載當前數據。一個醜陋的解決方案是隻做兩個下載按鈕，但我確定有一個優雅的解決方案。

這裏是我的代碼：

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

像這樣的東西應該工作：

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持有最後按下哪個按鈕，然後確定要下載的文件時使用該值。