[R-pkg-devel] best way the handle errors conditionally
On 06/03/2017 5:17 AM, Thierry Onkelinx wrote:
Dear all,
I'd like your advice on handling errors conditionally within a function.
Imagine a function that does several database operations. The user has the
option to run them inside a transaction. So the code has somewhere near the
top:
if (transaction) {
DBI::dbBegin(conn)
}
At the end of the function there is a command which commits the transaction.
if (transaction) {
DBI::dbCommit(conn)
}
If something goes wrong, one reverses the database operations by issuing
the DBI::dbRollback(conn) command. The first option for issuing that is to
use tryCatch(). The drawback is that the set of command can be a few
hundred lines, which harms readability when wrapping them into a tryCatch().
You could put the long set of commands into their own function, perhaps
locally defined within the main function. For example,
longset <- function() { ... }
if (transaction) {
DBI::dbBegin(conn)
}
tryCatch(
longset()
error = function(e){
if (transaction) {
dbRollback(conn)
}
stop(e)
}
)
Duncan Murdoch