Active bindings in attached environments
An explanation of this would be nice in ?makeActiveBinding, e.g., NOTE: When an environment is attach()'ed to the search path, any active bindings in it are not preserved as active bindings. This happens because attach() actually adds a new environment to the search path, and copies objects into it. Thus, active bindings are evaluated and their values copied into the attached environment. (Is this explanation correct?) -- Tony Plate (PS: Thunderbird wants to spell-correct "makeActiveBinding" to "vindictivenesses", which seems an amusingly appropriate allusion to the nature of this "gotcha" :-)
Jeffrey Horner wrote:
On Thu, Nov 5, 2009 at 9:53 AM, Jeffrey Horner <jeffrey.horner at gmail.com> wrote:
Hi,
Is this expected behavior for active bindings in attached
environments, or is this a bug:
e <- new.env()
makeActiveBinding('x',function() 'foo',e)
ls(e)
[1] "x"
attach(e)
search()
[1] ".GlobalEnv" "e" "package:graphics"
[4] "package:grDevices" "package:datasets" "package:utils"
[7] "package:methods" "Autoloads" "package:base"
x
function() 'foo'
Should this print 'foo' ? The following works as I would expect:
with(e,x)
[1] "foo"
but this doesn't:
f <- function() x
f()
function() 'foo'
However, changing the environment of f does:
environment(f) <- e
f()
[1] "foo"
Actually, it is my understanding of attach() which is the bug. The attach documentation clearly states that a copy of the object is attached, not the object itself. Thanks, Jeff -- http://biostat.mc.vanderbilt.edu/JeffreyHorner
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