R devel - May 2011 - Query super- and subclasses of a class: is there a better way than to use 'completeClassDefinition()'

Dear List,

when I first started to use S4 classes, I used the function 
'completeClassDef()' in order to see the super- and subclasses of a 
certain class:

setClass(Class="A", representation=list(a="numeric"))
setClass(Class="B", contains="A",
representation=list(b="character"))
# Super
x <- completeClassDefinition("B")
attributes(x)
names(x@contains)
# Sub
x <- completeClassDefinition("A")
attributes(x)
names(x@subclasses)

This also does the trick for Reference Classes for me. However, I 
re-read the respective section on the help page and wondered if I should 
be more careful about using this function for this purpose as the page says:
"|completeClassDefinition: |Completes the definition of |Class|, 
relative to the class definitions visible from environment |where|. If 
|doExtends| is |TRUE|, complete the super- and sub-class information. 
This function is called when a class is defined or re-defined."

So here are my questions:
1) Is it safe to call 'completeClassDef()' explicitly or can anything be
"overwritten" by this?
2) Is there a better way to query the super-/subclasses of a certain 
S4/Reference Class?

Best regards and I'd like to take this opportunity to express my 
gratitude to everyone on this list who takes the time to provide such 
great help!
Janko

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On 05/30/2011 08:54 AM, Janko Thyson wrote:
> Dear List,
>
> when I first started to use S4 classes, I used the function
> 'completeClassDef()' in order to see the super- and subclasses of a
> certain class:
Hi Janko -- I think 'complete' is meant as an adverb here; what you 
might want is names(getClassDef("A")@subclasses) (see 
slotNames(class(getClassDef("A"))) for other useful info).

Martin
>
> setClass(Class="A", representation=list(a="numeric"))
> setClass(Class="B", contains="A",
representation=list(b="character"))
> # Super
> x<- completeClassDefinition("B")
> attributes(x)
> names(x at contains)
> # Sub
> x<- completeClassDefinition("A")
> attributes(x)
> names(x at subclasses)
>
> This also does the trick for Reference Classes for me. However, I
> re-read the respective section on the help page and wondered if I should
> be more careful about using this function for this purpose as the page
says:
> "|completeClassDefinition: |Completes the definition of |Class|,
> relative to the class definitions visible from environment |where|. If
> |doExtends| is |TRUE|, complete the super- and sub-class information.
> This function is called when a class is defined or re-defined."
>
> So here are my questions:
> 1) Is it safe to call 'completeClassDef()' explicitly or can
anything be
> "overwritten" by this?
> 2) Is there a better way to query the super-/subclasses of a certain
> S4/Reference Class?
>
> Best regards and I'd like to take this opportunity to express my
> gratitude to everyone on this list who takes the time to provide such
> great help!
> Janko
>
>
>
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

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