Thank you very much! I'm using the first example.
For others: there are two simple typos in Henrik's email below: pretty sure
y <- this$.; should be y <- this$.y;
Thanks again...
Corrected below...
Ben
> Hello,
>
> I'd like to 'do work' on data members upon construction (i.e. without
> implementing it in a get method). Is this the best way to create data
member
> 'z' upon construction? I'm thinking if .z=paste(x,y) below gets more
complex
> I'll run into issues.
>
> setConstructorS3("MyClass", function(x=NA,y=NA,...) {
> this <- extend(Object(), "MyClass",
> .x=x,
> .y=y,
> .z=paste(x,y)
> )
Looks good to me and is standard R procedure where you work with the
*arguments*. You can also work on the object after it's been
instantiated, e.g.
setConstructorS3("MyClass", function(x=NA,y=NA,...) {
this <- extend(Object(), "MyClass",
.x=x,
.y=y,
.z=NULL
)
# Assign z
this$.z <- paste(this$.x, this$.y);
this;
})
Note that if .z always a function of .x and .y it is redundant. Then
an alternative is to create it on the fly, i.e.
setMethodS3("getZ", "MyClass", function(this, ...) {
x <- this$.x;
y <- this$.y;
z <- paste(x, y);
z;
})
You can then make it clever and cache the results so that it is only
calculated once, e.g.
setMethodS3("getZ", "MyClass", function(this, ...) {
z <- this$.z;
if (is.null(z)) {
x <- this$.x;
y <- this$.y;
z <- paste(x, y);
this$.z <- z;
}
z;
})
However, you then have to make sure to reset z (this$.z <- NULL)
whenever .x or .y is changed.
/Henrik
On Thu, Sep 22, 2011 at 10:18 AM, Henrik Bengtsson <h...@biostat.ucsf.edu>wrote:
> On Thu, Sep 22, 2011 at 9:06 AM, Ben qant <ccqu...@gmail.com> wrote:
> > Hello,
> >
> > I'd like to 'do work' on data members upon construction (i.e. without
> > implementing it in a get method). Is this the best way to create data
> member
> > 'z' upon construction? I'm thinking if .z=paste(x,y) below gets more
> complex
> > I'll run into issues.
> >
> > setConstructorS3("MyClass", function(x=NA,y=NA,...) {
> > this <- extend(Object(), "MyClass",
> > .x=x,
> > .y=y,
> > .z=paste(x,y)
> > )
>
> Looks good to me and is standard R procedure where you work with the
> *arguments*. You can also work on the object after it's been
> instantiated, e.g.
>
> setConstructorS3("MyClass", function(x=NA,y=NA,...) {
> this <- extend(Object(), "MyClass",
> .x=x,
> .y=y,
> .z=NULL
> )
>
> # Assign z
> this$.z <- paste(this$.x, this$.y);
>
> this;
> })
>
> Note that if .z always a function of .x and .y it is redundant. Then
> an alternative is to create it on the fly, i.e.
>
> setMethodS3("getZ", "MyClass", function(this, ...) {
> x <- this$.x;
> y <- this$.;
> z <- paste(x, y);
> z;
> })
>
> You can then make it clever and cache the results so that it is only
> calculated once, e.g.
>
> setMethodS3("getZ", "MyClass", function(this, ...) {
> z <- this$.z;
> if (is.null(z)) {
> x <- this$.x;
> y <- this$.;
> z <- paste(x, y);
> this$.z <- z;
> }
> z;
> })
>
> However, you then have to make sure to reset z (this$.z <- NULL)
> whenever .x or .y is changed.
>
> /Henrik
>
> >
> > })
> > setMethodS3("getX", "MyClass", function(this, ...) {
> > this$.x;
> > })
> > setMethodS3("getY", "MyClass", function(this, ...) {
> > this$.y;
> > })
> > setMethodS3("getZ", "MyClass", function(this, ...) {
> > this$.z;
> > })
> >
> >> mc = MyClass('a','b')
> >> mc$x
> > [1] "a"
> >> mc$y
> > [1] "b"
> >> mc$z
> > [1] "a b"
> >
> >
> > Thanks,
> >
> > ben
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > 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]]
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