Checks if an R object exists on the server-side

This function checks that a specified data object exists or has been correctly created on a specified set of data servers.

ds.testObjExists(test.obj.name = NULL, datasources = NULL)

Arguments

test.obj.name

a character string specifying the name of the object to search.

datasources

a list of DSConnection-class objects obtained after login. If the datasources argument is not specified the default set of connections will be used: see datashield.connections_default.

Value

ds.testObjExists returns a list of messages specifying that the object exists on the server-side. If the specified object does not exist in at least one of the specified data sources or it exists but is of class NULL, the function returns an error message specifying that the object does not exist in all data sources.

Details

Close copies of the code in this function are embedded into other functions that create an object and you then wish to test whether it has successfully been created e.g. ds.make or ds.asFactor.

Server function called: testObjExistsDS

Author

DataSHIELD Development Team

Examples

if (FALSE) {
  ## Version 6, for version 5 see the Wiki
  
  # connecting to the Opal servers

  require('DSI')
  require('DSOpal')
  require('dsBaseClient')

  builder <- DSI::newDSLoginBuilder()
  builder$append(server = "study1", 
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM1", driver = "OpalDriver")
  builder$append(server = "study2", 
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM2", driver = "OpalDriver")
  builder$append(server = "study3",
                 url = "http://192.168.56.100:8080/", 
                 user = "administrator", password = "datashield_test&", 
                 table = "CNSIM.CNSIM3", driver = "OpalDriver")
  logindata <- builder$build()
  
  connections <- DSI::datashield.login(logins = logindata, assign = TRUE, symbol = "D") 
  
  #Check if D object exists on the server-side
  
  ds.testObjExists(test.obj.name = "D",
                   datasources = connections)
 
  # Clear the Datashield R sessions and logout                 
  datashield.logout(connections) 
  
}