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% File src/library/base/man/taskCallbackNames.Rd
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2016 R Core Team
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% Distributed under GPL 2 or later
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\name{taskCallbackNames}
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\alias{getTaskCallbackNames}
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\title{Query the Names of the Current Internal Top-Level Task Callbacks}
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\description{
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  This provides a way to get the names (or identifiers)
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  for the currently registered task callbacks
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  that are invoked at the conclusion of each top-level task.
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  These identifiers can be used to remove a callback.
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}
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\usage{
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getTaskCallbackNames()
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}
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\value{
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  A character vector giving the name for each of the
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  registered callbacks which are invoked when
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  a top-level task is completed successfully.
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  Each name is the one used when registering
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  the callbacks and returned as the in the
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  call to \code{\link{addTaskCallback}}.
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}
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\note{
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  One can use \code{\link{taskCallbackManager}}
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  to manage user-level task callbacks,
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  i.e., S-language functions, entirely within
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  the S language and access the names
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  more directly.
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}
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\seealso{
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  \code{\link{addTaskCallback}},
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  \code{\link{removeTaskCallback}},
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  \code{\link{taskCallbackManager}}
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  \url{https://developer.r-project.org/TaskHandlers.pdf}
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}
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\examples{
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 n <- addTaskCallback(function(expr, value, ok, visible) {
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                        cat("In handler\n")
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                        return(TRUE)
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                      }, name = "simpleHandler")
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 getTaskCallbackNames()
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   # now remove it by name
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 removeTaskCallback("simpleHandler")
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 h <- taskCallbackManager()
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 h$add(function(expr, value, ok, visible) {
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                        cat("In handler\n")
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                        return(TRUE)
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                      }, name = "simpleHandler")
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 getTaskCallbackNames()
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 removeTaskCallback("R-taskCallbackManager")
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}
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\keyword{environment}