Hi Christophe --
[EMAIL PROTECTED] writes:
Hi the list.
I try to learn the S4 programming. I find the wiki and several doc. But
I still have few questions...
1. To define 'representation', we can use two syntax :
- representation=list(temps = 'numeric',traj = 'matrix')
- representation(temps = 'numeric',traj = 'matrix')
Is there any difference ?
See the help page for representation
?representation
for a description of the checks performed by this function. View the
function definition for 'representation' with
representation
to see the implementation details.
2. 'validityMethod' check the intialisation of a new object, but not
the latter
modifications. Is it possible to set up a validation that check every
modifications ?
No. A solution is to create 'setters' that use slot- or @- and then
check validity explicitly; the 'user' would then invoke the setters
and avoid direct slot access..
3. When we use setMethod('initialize',...) does the validityMethod
become un-used ?
'initialize' for signature .Object=ANY calls validObject sometimes
(when length(list(...))0; see
getMethod(initialize, ANY)
for implementation details). So if your 'initialize' uses
callNextMethod (I think object oriented practice would encourage this)
and the appropriate conditions apply, then validity gets called. Some
'initialize' paradigms might not work very well with this setup, e.g.,
.Object - callNextMethod() # validObject
# further modify .Object and hence check validity again??
4. Is it possible to set up several initialization processes ? One
that build an objet from a data.frame, one from a matrix...
No, 'initialize' has only a single argument to dispatch on (.Object,
based on the prototype of the object being created) and so cannot be
specialized for additional arguments. Solutions include writing
conditional code within your 'initialize', or to create a new
'constructor' generic with it's own signature that performs initial
coercion before calling 'new'. Personally I think this is a good
solution, treating 'new' and 'initialize' as internal functions that
the 'user' does not invoke directly.
Hope that helps,
Martin
Thanks
Christophe
Ce message a ete envoye par IMP, grace a l'Universite Paris 10 Nanterre
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--
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109
Location: Arnold Building M2 B169
Phone: (206) 667-2793
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