Retrieve print function code for an S4 class/object - r

Question

I am working with an S4 object (PairwiseAlignmentsSingleSubject). When I type the name of an instance of this class into the console and hit enter, I get something like the following:
Global PairwiseAlignmentsSingleSubject (1 of 1)
pattern: ATCGATCGATCGATCG
subject: -TCGATCG-TCGATC-
score: -16.23717
The actual class is much larger than just this, so I assume some print function for the class is being called. I really want to see the code used in this print function, but I cannot figure out how to pull it up. Could someone please offer some insights into this?
Thank you
Edit based on JDL's answer:
I was able to use selectMethod (I guess this class inherits its "print" function). However, the result is just:
> selectMethod("print",signature(x="BioStrings"))
Method Definition (Class "derivedDefaultMethod"):
function (x, ...)
UseMethod("print")
<bytecode: 0x5572111b6d58>
<environment: namespace:base>
Signatures:
x
target "BioStrings"
defined "ANY"
Which is still not very informative and definitely not the full code for the function. Does anyone know how I can take this further?

Answer 1

To get the code associated with a method, the function to use is getMethod. If you know the class you are interested in then the call is of the form below
getMethod("print",signature(x="numeric"))
which in your specific case is
getMethod("print",signature(x="PairwiseAlignmentsSingleSubject")).
If you have an object obj and want to see what code will be applied to it when you call print, then a slight modification allows this:
getMethod("print",signature(x=class(obj)))
This also works for any generic function, you can substitute "plot" etc. in place of "print".
Note that this only works for methods defined for the exact class you specified. If there isn't such a method (i.e. one based on inheritance was used instead), then replace getMethod with selectMethod.
For further information, consult the help page at ?getMethod which documents these and some similar functions.

Answer 2

Looking through their github is usually useful :)
They don't use 'print' but 'show'.
If you look at the source code for the class PairwiseAlignmentsSingleSubject you can see a show method, but it's only for the class PairwiseAlignmentsSingleSubjectSummary.
But in the last method for 'PairwiseAlignmentsSingleSubject' you see it creates a 'newPairwiseAlignments' and if you look a the source code for the class PairwiseAlignments you'll find the "show" method starting at line 398.
### - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
### The "show" method
###
### TODO: Maybe make the "show" method format the alignment in a SGD fashion
### i.e. split in 60-letter blocks and use the "|" character to highlight
### exact matches.
###
.show_PairwiseAlignments <- function(x)
{
x_len <- length(x)
if (x_len == 0L)
cat("Empty ")
cat(switch(type(x), "global"="Global", "overlap"="Overlap",
"local"="Local", "global-local" = "Global-Local",
"local-global"="Local-Global"),
" ", class(x), sep="")
if (x_len == 0L) {
cat("\n")
return()
}
cat(" (1 of ", x_len, ")\n", sep="")
x1 <- x[1L]
x_type <- type(x)
global.pattern <- x_type %in% c("global", "global-local")
global.subject <- x_type %in% c("global", "local-global")
p1start <- if (global.pattern)
""
else
paste0("[", start(x1#pattern#range), "]")
s1start <- if (global.subject)
""
else
paste0("[", start(x1#subject#range), "]")
width <- max(nchar(p1start), nchar(s1start))
if (width != 0L) {
width <- width + 1L
p1start <- format(p1start, justify="right", width=width)
s1start <- format(s1start, justify="right", width=width)
}
width <- getOption("width") - 9L - width
pattern1 <- toSeqSnippet(alignedPattern(x1)[[1L]], width)
subject1 <- toSeqSnippet(alignedSubject(x1)[[1L]], width)
cat("pattern:", p1start, " ", add_colors(pattern1), "\n", sep="")
cat("subject:", s1start, " ", add_colors(subject1), "\n", sep="")
cat("score:", score(x1), "\n")
}
setMethod("show", "PairwiseAlignments",
function(object) .show_PairwiseAlignments(object)
)