Pass user input vector to a function that takes a string - r

Question

I have a shiny app that takes in user input:
input$libraries is a reactive character vector produced by user input from
output$libraries <- renderUI({
checkboxGroupInput(inputId = "libraries",
label = strong("Select the libraries for which you would like to see part counts"),
choiceValues = LibraryIDs$libraryid,
choiceNames = LibraryNames$name,
selected = LibraryIDs$libraryid[1],
inline = T)}})
})
I would like to select from my postgreSQL database, I have a function set up as such:
get_query <- function(querystring){
# create a connection
# loads the PostgreSQL driver
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "RosettaRelational",
host = "localhost", port = 5432,
user = "postgres", password = rstudioapi::askForPassword("Database password"))
on.exit(dbDisconnect(con))
# check for the existance of tables, must be created in pgAdmin4
#dbExistsTable(con, "libraries")
query <- eval(parse(text = querystring))
return(query)
}
It takes in a string and parses it to evaluate the query
now when I try to query the database as such:
Names <- get_query(paste0("con %>% tbl('libraries') %>%
filter(libraryid %in% input$libraries) %>% select(name) %>% collect()"))
I get the error: object 'input' not found. I know it's not parsing the reactive character vector correctly. How should I change this to get it to work?
I tried:
Names <- get_query(paste0("con %>% tbl('libraries') %>%
filter(libraryid %in% '",input$libraries,"') %>% select(name) %>% collect()"))
but that only selects the first library in the vector even when the user selects multiple libraries..this works when input$ is only one character, for example when the input is an action button instead of checkboxes
basically what I need is for input$libraries to look like c('111a,'111b','211','311a') when it is passed into the string if user selects 111a, 111b, 211 and 311a, instead of just '111a' which is what it is currently passing.

Answer 1

It seems from some testing on my side that your code
Names <- get_query(paste0("con %>% tbl('libraries') %>% filter(libraryid %in% '",input$libraries,"') %>% select(name) %>% collect()"))
will "vectorise" in its current form for multiple libraries in input$libraries. This will create a separate string for each library in input$libraries instead of one string containing all libraries. e.g.
> Names
[1] "con %>% tbl('libraries') %>% filter(libraryid %in% '111a') %>% select(name) %>% collect()"
[2] "con %>% tbl('libraries') %>% filter(libraryid %in% '111b') %>% select(name) %>% collect()"
Using my own data and your suggestion "for input$libraries to look like c('111a','111b','211','311a')" I adapted your code to
Names <- get_query(paste0("con %>% tbl('libraries') %>% filter(libraryid %in% c(", paste0("'", input$libraries, "'", collapse = ", "), ")) %>% select(name) %>% collect()"))
This should give you your required c('111a', '111b', '211', '311a').
It's not the most elegant but it should work. You could also do that inner paste0() before if it looks messy, as below
libraries_comma_separated <- paste0("'", input$libraries, "'", collapse = ", ")
This will give you '111a', '111b', '211', '311a' and then do
Names <- get_query(paste0("con %>% tbl('libraries') %>% filter(libraryid %in% c(", libraries_comma_separated, ")) %>% select(name) %>% collect()"))