[R] handling a cancelled file.choose()

[Ben Tupper]

Deepayan Sarkar wrote:
> On 6/6/07, Ben Tupper <btupper at bigelow.org> wrote:
>> Hello,
>>
>>
>> I have a file reading function that prompts the user with a file dialog
>> if a filename is not provided in the argument list.  It is desirable to
>> return gracefully if the user selects "Cancel", but file.choose() throws
>> an error instead of returning something like a character.
>>
>>  > file.choose()
>> [1] "/Users/ben/ben_idl.pref"
>>
>>  > file.choose()
>> Error in file.choose() : file choice cancelled
>>
>> I naively planned to use nchar() to test the length, assuming
>> cancellation would return a zero-length character. That appears to be
>> out of the question. [...]
> 
> Not really, errors can be caught and handled. This seems to give the
> behaviour you want:
> 
> tryCatch(file.choose(), error = function(e) "")
> 
> -Deepayan

Thanks all,

I am very pleased to know about conditions in the base package.  Slick!

Ben