[R] how to override/replace a function in a package namespace?

[Ben Bolker]

Henrik Bengtsson <hb <at> stat.berkeley.edu> writes:

> 
> The few times I want to patch a function like this, I use:
> 
>   unlockBinding(name, env);
>   assignInNamespace(name, value, ns=pkgName, envir=env);
>   assign(name, value, envir=env);
>   lockBinding(name, env);
> 
> /Henrik
> 

  OK, I admit that I don't get it.
  I eventually managed to figure out that I needed the
environment corresponding to getNamespace("package")
in this case, not the one corresponding to 
as.environment("package"), but I still seem to
be doing something wrong (perhaps I'm following the
recipe too mindlessly).

  The goal here is to replace a bit of code
that uses parent.frame(2) with parent.frame(1) --
that's what my "rjhack.file" does.


tstf <- function() {
  print(environment(jags))
  a = grep("get,",deparse(jags),value=TRUE)  ## parent.frame(2)
  length(grep("1",a))>0
}

library(R2jags)
tstf()

rjhack.file <- "~/lib/R/pkgs/mixstock/pkg/inst/myjags.R"
source(rjhack.file)  ## read hacked version into global workspace
tstf()
RJ <- getNamespace("R2jags")
## attempt to replace package version with hacked version ...
unlockBinding("jags", RJ)
assignInNamespace("jags",jags,ns="R2jags", envir=RJ)
assign("jags", jags, envir=RJ)
lockBinding("jags",RJ)
rm(jags) ## get rid of global copy


  I'm beginning to feel it would be a lot easier
to build my own local copy of the package ... in
what way am I being a bonehead?
  
library(fortunes)
gsub("S4 methods","namespaces",fortune("S4")[1])

  thanks
    Ben Bolker