which OO programming style in R will result readab

问题:

I'm author of the logging package on CRAN, I don't see myself as an R programmer, so I tried to make it as code-compatible with the Python standard logging package as I could, but now I have a question. and I hope it will give me the chance to learn some more R!

it's about hierarchical loggers. in Python I would create a logger and send it logging records:

l = logging.getLogger("some.lower.name")
l.debug("test")
l.info("some")
l.warn("say no")

In my R package instead you do not create a logger to which you send messages, you invoke a function where one of the arguments is the name of the logger. something like

logdebug("test", logger="some.lower.name")
loginfo("some", logger="some.lower.name")
logwarn("say no", logger="some.lower.name")

the problem is that you have to repeat the name of the logger each time you want to send it a logging message. I was thinking, I might create a partially applied function object and invoke that instead, something like

logdebug <- curry(logging::logdebug, logger="some.lower.logger")

but then I need doing so for all debugging functions...

how would you R users approach this?

回答1:

Sounds like a job for a reference class ?setRefClass, ?ReferenceClasses

Logger <- setRefClass("Logger",
                  fields=list(name = "character"),
                  methods=list(
                    log = function(level, ...) 
                          { levellog(level, ..., logger=name) },
                    debug = function(...) { log("DEBUG", ...) },
                    info = function(...) { log("INFO", ...) },
                    warn = function(...) { log("WARN", ...) },
                    error = function(...) { log("ERROR", ...) }
                    ))

and then

> basicConfig()
> l <- Logger$new(name="hierarchic.logger.name")
> l$debug("oops")
> l$info("oops")
2011-02-11 11:54:05 NumericLevel(INFO):hierarchic.logger.name:oops
> l$warn("oops")
2011-02-11 11:54:11 NumericLevel(WARN):hierarchic.logger.name:oops
> 

回答2:

This could be done with the proto package. This supports older versions of R (its been around for years) so you would not have a problem of old vs. new versions of R.

library(proto)
library(logging)

Logger. <- proto(
        new = function(this, name)
            this$proto(name = name),
        log = function(this, ...) 
            levellog(..., logger = this$name),
        setLevel = function(this, newLevel) 
            logging::setLevel(newLevel, container = this$name),
        addHandler = function(this, ...)
            logging::addHandler(this, ..., logger = this$name), 
        warn = function(this, ...)
            this$log(loglevels["WARN"], ...),
        error = function(this, ...)
            this$log(loglevels["ERROR"], ...) 
)
basicConfig()
l <- Logger.$new(name = "hierarchic.logger.name")
l$warn("this may be bad")
l$error("this definitely is bad")

This gives the output:

> basicConfig()
> l <- Logger.$new(name = "hierarchic.logger.name")
> l$warn("this may be bad")
2011-02-28 10:17:54 WARNING:hierarchic.logger.name:this may be bad
> l$error("this definitely is bad")
2011-02-28 10:17:54 ERROR:hierarchic.logger.name:this definitely is bad

In the above we have merely layered proto on top of logging but it would be possible to turn each logging object into a proto object, i.e. it would be both, since both logging objects and proto objects are R environments. That would get rid of the extra layer.

See the http://r-proto.googlecode.com for more info.

回答3:

Why would you repeat the name? It would be more convenient to pass the log-object directly to the function, ie

logdebug("test",logger=l)
# or
logdebug("test",l)

A bit the way one would use connections in a number of functions. That seems more the R way of doing it I guess.