That is really helpful. I am trying to get the rmatch function to return the position of the 'name' instead of the value. So rmatch(app, "FirsKey") would return c(3,3,1). Then app[[c(3,3,1)]] <- 'new value' would be perfect.
On Tue, Dec 30, 2014 at 6:43 AM, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 29/12/2014 4:41 PM, Daniel Gabrieli wrote: > > I cross posted this on Stack Overflow: > > > http://stackoverflow.com/questions/27694466/chaining-multiple-replacement-functions-in-r > > > > > > I am using R to work with a large JS object (using the library rjsonio). > As > > such, I have a lot of nested lists, which are getting somewhat cumbersome > > to work with. I have a simplified example below. I am trying to work with > > this object by creating some form of ‘getter’ and ‘setter’ functions. > After > > looking around, I have found a pretty nice ‘getter’ function that > recurses > > through the object and returns the value for the first matching label. > This > > is especially great because it lends itself to chaining functions > together. > > However, I can not figure out a way to get the same effect for a ‘setter’ > > function. Any thoughts on how to create a ‘setter’ function that can be > > chained together in a similar fashion? > > I haven't worked through the details here so this might not work, but > the assignment function could add extra information saying which part of > the object was modified. In the example below, "Firstkey" is > app[[c(3,3,1)]], so a function that modified it could attach c(3,3,1) as > an attribute, and later functions that wanted to do more things to it > could start looking there. > > I guess the tricky part would be getting rid of that attribute if you > didn't want to pass it along the chain, e.g. the final call shouldn't > return it. > > Duncan Murdoch > > > > > #example, simplified, object > > app = list( > > 1, > > 2, > > d=list(a=123, > > b=456, > > list( > > FirstKey=list(attr1='good stuff', attr2=12345), > > SecondKey=list(attr1='also good stuff', attr2=4321) > > ) > > ) > > ) > > > > > > #Return a function that returns the value > > #associated with first label that matches 'name' > > getByName <- function(name){ > > rmatch <- function(x) { > > pos <- match(name, names(x)) > > if (!is.na(pos)) > > return(x[[pos]]) > > for (el in x) { > > if (class(el) == "list") { > > out <- Recall(el) > > if (!is.null(out)) return(out) > > } > > } > > } > > rmatch > > } > > > > getFirstKey <- getByName("FirstKey") > > getAttr1 <- getByName("attr1") > > getAttr2 <- getByName("attr2") > > > > #I like that I can chain these functions together > > getAttr1(getFirstKey(app)) > > getAttr2(getFirstKey(app)) > > > > # I would like to be able to do something like this > > # But this won't work > > ### getAttr1(getFirstKey(app)) <- 9876 > > > > # This does work,,, but I loose the ability to chain functions together > > # Closure around a replacement function > > setterKeyAttr <- function(keyName, attr){ > > function(x, value){ > > x$d[[3]][[keyName]][[attr]] <- value > > x > > } > > } > > > > `setFirstKeyAttr2<-` <- setterKeyAttr("FirstKey", "attr2") > > setFirstKeyAttr2(app) <- 22222 > > #check the answer is correct > > getAttr2(getFirstKey(app)) > > > > > > > > references: > > > > > http://stackoverflow.com/questions/23124096/r-decorator-to-change-both-input-and-output > > > > > http://r.789695.n4.nabble.com/How-to-get-a-specific-named-element-in-a-nested-list-td3037430.html > > > > http://adv-r.had.co.nz/Functions.html > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
