Hey that helps! Wish we could also throw an error if both were missing...
Thanks again!
Ben
On Mon, Aug 8, 2011 at 4:37 PM, Henrik Bengtsson <h...@biostat.ucsf.edu>wrote:
> Hi,
>
> you can do something like:
>
> setConstructorS3("Person", function(name, age) {
> # Check for missing arguments, but allow for empty
> # constructor calls, i.e. Person().
> if (missing(name) && missing(age)) {
> name <- NA;
> age <- NA;
> } else if (missing(name)) {
> throw("Argument 'name' is missing.");
> } else if (missing(age)) {
> throw("Argument 'age' is missing.");
> }
>
> extend(Object(), "Person",
> .name=name,
> .age=age
> )
> })
>
> /Henrik
>
> On Tue, Aug 9, 2011 at 12:21 AM, Ben qant <ccqu...@gmail.com> wrote:
> > Hello,
> >
> > Using the R.oo package, how do I throw an error if a field is not present
> > when the user of the class creates the object?
> >
> > Using the example in the R.oo package:
> >
> > setConstructorS3("Person", function(name, age) {
> > if (missing(name)) name <- NA;
> > if (missing(age)) age <- NA;
> >
> > extend(Object(), "Person",
> > .name=name,
> > .age=age
> > )
> > })
> >
> > [rest of class methods here...etc...]
> >
> > User types this with no issues because both age and name are there:
> >
> > p1 <- Person("Dalai Lama", 67)
> >
> > User types this and I want it to throw an error because the age field is
> > missing:
> >
> > p1 <- Person("Dalai Lama")
> >
> > Link to the example I am drawing from:
> > http://127.0.0.1:22346/library/R.oo/html/Object.html
> >
> > I know how to throw an error when a method is used. I want to throw an
> error
> > when the object is created.
> >
> > I've tried print and cat statements in the Constructor section and after
> the
> > extend statement.
> >
> > 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.
> >
>
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