R help - Nov 2018 - The Suggests field in a DESCRIPTION file.

I am building a package which contains a function from which I wish to 
call the fortune() function from the fortunes package --- if that 
package is available.

I have place the line

    Suggests: fortunes

in the DESCRIPTION file.

In my code for the function that I am writing (let's call it
"foo")
I put
> fortOK <- requireNamespace(fortunes,quietly=TRUE)
>         if(fortOK) {
>             fortunes::fortune()
>         }
thinking that I was following all of the prescriptions in "Writing R 
Extensions".  Yet when I do R CMD check on the package I get
> * checking R code for possible problems ... NOTE
> foo: no visible binding for global variable ?fortunes?
> Undefined global functions or variables:
>   fortunes
What am I doing wrong?

Thanks for any insight.

cheers,

Rolf Turner

P. S.  I tried putting an "imports(fortunes)" in the NAMESPACE file,
but
this just made matters worse:
> * checking package dependencies ... ERROR
> Namespace dependency not required: ?fortunes?
Huh?  What on earth is this actually saying?  I cannot parse this error 
message.

R. T.

-- 
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276

I figured it out.  The package name in the call to requireNamespace() 
has to be a *text string*.  I should've had:

     fortOK <- requireNamespace("fortunes",quietly=TRUE)

So require() takes a package name, but requireNamespace() takes a 
*string* specifying the package name.  Trap for young players.

Psigh.

cheers,

Rolf Turner

On 11/18/18 11:16 AM, Rolf Turner wrote:
> 
> I am building a package which contains a function from which I wish to 
> call the fortune() function from the fortunes package --- if that 
> package is available.
> 
> I have place the line
> 
>  ?? Suggests: fortunes
> 
> in the DESCRIPTION file.
> 
> In my code for the function that I am writing (let's call it
"foo")
> I put
> 
>> fortOK <- requireNamespace(fortunes,quietly=TRUE)
>> ??????? if(fortOK) {
>> ??????????? fortunes::fortune()
>> ??????? }
> 
> thinking that I was following all of the prescriptions in "Writing R 
> Extensions".? Yet when I do R CMD check on the package I get
> 
>> * checking R code for possible problems ... NOTE
>> foo: no visible binding for global variable ?fortunes?
>> Undefined global functions or variables:
>> ? fortunes
> 
> What am I doing wrong?
> 
> Thanks for any insight.
> 
> cheers,
> 
> Rolf Turner
> 
> P. S.? I tried putting an "imports(fortunes)" in the NAMESPACE
file, but
> this just made matters worse:
> 
>> * checking package dependencies ... ERROR
>> Namespace dependency not required: ?fortunes?
> 
> Huh?? What on earth is this actually saying?? I cannot parse this error 
> message.
> 
> R. T.
> 

-- 
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276