taskCallbackNames            package:base            R Documentation

Query the names of the current internal top-level task callbacks

Description:

     This provides a way to get the names (or identifiers) for the
     currently registered task callbacks that are invoked at the
     conclusion of each top-level task. These identifiers can be used
     to remove a callback.

Usage:

     getTaskCallbackNames()

Value:

     A character vector giving the name for each of the registered
     callbacks which are invoked when a top-level task is completed
     successfully. Each name is the one used when registering the
     callbacks and returned as the in the call to 'addTaskCallback'.

Note:

     One can use 'taskCallbackManager' to manage user-level task
     callbacks, i.e., S-language functions, entirely within the S
     language and access the names more directly.

See Also:

     'addTaskCallback', 'removeTaskCallback', 'taskCallbackManager'\
     <URL: http://developer.r-project.org/TaskHandlers.pdf>

Examples:

      n <- addTaskCallback(function(expr, value, ok, visible) {
                             cat("In handler\n")
                             return(TRUE)
                           }, name = "simpleHandler")

      getTaskCallbackNames()

        # now remove it by name
      removeTaskCallback("simpleHandler")

      h <- taskCallbackManager()
      h$add(function(expr, value, ok, visible) {
                             cat("In handler\n")
                             return(TRUE)
                           }, name = "simpleHandler")
      getTaskCallbackNames()
      removeTaskCallback("R-taskCallbackManager")

