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Error when assigning value in environment which is a locked binding

3 messages · Winston Chang, Simon Urbanek

Original
Winston Chang
# 
If an environment x contains a locked binding y which is also an
environment, and then you try to assign a value to a binding inside of
y, it can either succeed or fail, depending on how you refer to
environment y.

x <- new.env()
x$y <- new.env()
lockEnvironment(x, bindings = TRUE)

# This assignment fails
x$y$z <- 1
# Error in x$y$z <- 1 : cannot change value of locked binding for 'y'

# Saving x$y to another variable, and then assigning there works
y2 <- x$y
y2$z <- 10  # OK
print(x$y$z)
# 10


Is this a bug or a feature? I realize that x$y is a locked binding
while y2 is not.

-Winston
Simon Urbanek
#
On Aug 10, 2014, at 10:07 PM, Winston Chang <winstonchang1 at gmail.com> wrote:

            

      
      
      
    

        
Why?

In both cases (including your previous post) the you have two separate assignments: (x$y)$z <-1 followed by x$y <- y. So the first one always succeeds since there is no reason for it not to, but the second one doesn't because the binding is locked. 

I presume the confusion comes from the fact that environments are mutable, so x$y changes even if it was not assigned so it's irrelevant if the second assignment succeeds or not.

Cheers,
Simon