How to dynamically extract data from quandl in r shiny?

Question

I'm using the following code but it is giving me error.

textInput(inputId = "metadata",label = "Please select the company you want information about")

observe({
  if(is.null(input$metadata))
    return(NULL)
     Quandl.api_key("qZAzm6zea4nVK69ztzDJ")
     company=input$metadata
     dat=paste("NSE/",company,sep="")
     #b="NSE/TCS"
     data=Quandl(dat,type = "ts")
})