下拉列表R中的列名称来自数据库的Shiny SelectInput

Question

I am using the below code to populate the dropdown with database values:-

Server.R

sqlOutputAssetClass <- reactive({
    sqlInputAssetClass<- paste("select distinct ASSET_CLASS from DUMMY_TABLE",sep="")
    dbGetQuery(con, sqlInputAssetClass)
   })

sqlOutputFeedSrcSys <- eventReactive(input$pick_assetclass, {
    sqlInputFeedSrcSys<- paste("select distinct FEED_SRC_SYS from DUMMY_TABLE where ASSET_CLASS=",
                               "'",
                               input$pick_assetclass,"'",sep="")
    dbGetQuery(con,sqlInputFeedSrcSys)
    })        

observe ({
    updateSelectInput(session,"pick_assetclass","ASSET CLASS",
                      choices = sqlOutputAssetClass())
   })

observe ({
    updateSelectInput(session,"pick_feedsrcsys","FEED SOURCE SYSTEM",
                      choices = sqlOutputFeedSrcSys())
   })

UI.R

selectInput('pick_assetclass',label ='Asset Class',
            choices=NULL,selected = NULL, multiple = FALSE,width="450px"),

selectInput('pick_feedsrcsys',label ='Feed Src Sys',
            choices=NULL,selected = NULL, multiple = FALSE,width="450px"),

I see the dropdowns are filled with values but also the column names in the database table. Another strange thing is that when there is just one value in the dropdown then the value doesn't display but the column name displays.

Could you please let me know how to resolve these issues?

Thanks,

Answer 1

This is not an answer but an extended comment.

In order to see what values are passed to updateSelectInput , you can put a call to browser() just before the update like so

observe ({
  choices = sqlOutputAssetClass()
  browser()
  updateSelectInput(session,"pick_assetclass","ASSET CLASS",
                   choices = sqlOutputAssetClass()
  )
})

this will open an interactive console where you can print your choices as well as all other inputs/reactives and see which changes are necessary to convert it to a "bare" character sting without labels, attributes or names. This console will block the console until you click "next" and will be reopened whenever the observe block is run.

The object you eventually want to pass to the update function should look like this

choices <- c("FX", "CS", "AT", "FUTURES")

Answer 2

From ?selectInput :

choices: ... This can also be a named list whose elements are (either named or unnamed) lists or vectors. If this is the case, the outermost names will be used as the "optgroup" label for the elements in the respective sublist. This allows you to group and label similar choices. ...

So in your case, dbGetQuery is likely returning a named vector. Just run it through unname to strip those names before returning from sqlOutputAssetClass and the category names should go away:

sqlOutputAssetClass <- reactive({
    sqlInputAssetClass<- paste("select distinct ASSET_CLASS from DUMMY_TABLE",sep="")
    unname(dbGetQuery(con, sqlInputAssetClass))
   })