Embed reactively generated URL in shiny - r

Question

I would like to show in my shiny app a link that directs to the URL generated based on user's input. I don't want to show the full text of the URL. I know the a(href="",label="") function can be used if I know the URL beforehand, but in this case the URL depends on the user's input. The following doesn't work:
ui <- fluidPage(
titlePanel("Show map of a given state"),
sidebarLayout(
sidebarPanel(
textInput("state", label = "State", value = "CA", placeholder = "California or CA"),
actionButton("showU","Show map")
),
mainPanel(
conditionalPanel(
condition = "input.showU > 0",
htmlOutput("url"),
a(href=htmlOutput("url"),"Show in Google Map",target="_blank")
)
)
)
)
server <- function(input, output){
observeEvent(input$showU,{
output$url <-renderUI({paste("https://www.google.com/maps/place/", input$state, sep="")})
})
}
shinyApp(ui,server)
I hope I can click on the "Show in Google Map" and be directed to the URL generated on the fly. Please help me, thank you.

Answer 1

You need to use renderUI together with uiOutput to update UI reactively:
library(shiny)
ui <- fluidPage(
titlePanel("Show map of a given state"),
sidebarLayout(
sidebarPanel(
textInput("state", label = "State", value = "CA", placeholder = "California or CA"),
actionButton("showU","Show map")
),
mainPanel(
conditionalPanel(
condition = "input.showU > 0",
uiOutput("url")
)
)
)
)
server <- function(input, output){
observeEvent(input$showU,{
output$url <-renderUI(a(href=paste0('https://www.google.com/maps/place/', input$state),"Show in Google Map",target="_blank"))
})
}
shinyApp(ui,server)

Answer 2

If this questions is actually about creating reactive URL links, then HubertL's answer is the way to go.
If you want to keep the map and search funciton all self-contained in the shiny, rather than having to open a new link to Google Maps, you can use my googleway package to achieve the same task
library(shiny)
library(googleway)
ui <- fluidPage(
titlePanel("Show map of a given state"),
sidebarLayout(
sidebarPanel(
),
mainPanel(
google_mapOutput(outputId = "myMap", height = "600px")
)
)
)
server <- function(input, output){
## you need a valid API key from Google Maps
## https://developers.google.com/maps/
map_key <- "your_map_api_key"
output$myMap <- renderGoogle_map({
google_map(key = map_key, search_box = T)
})
}
shinyApp(ui,server)

Answer 3

I used a HTML button for which the url could be generated recursively
library(shiny)
# Define UI for application that draws a histogram
ui <- fluidPage(
# Application title
titlePanel("HTML button"),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
sliderInput("bins",
"Number of bins:",
min = 1,
max = 50,
value = 30)
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot"),
HTML(paste0(htmlOutput('url_test')))
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output) {
output$distPlot <- renderPlot({
# generate bins based on input$bins from ui.R
x <- faithful[, 2]
bins <- seq(min(x), max(x), length.out = input$bins + 1)
# draw the histogram with the specified number of bins
hist(x, breaks = bins, col = 'darkgray', border = 'white')
})
output$url_test = renderText({
paste('Go to Google')
})
cultivar_url = reactive({
print('https://www.google.com')
})
}
# Run the application
shinyApp(ui = ui, server = server)