std.getopt: checking if an option has been passed

[Laeeth Isharc via Digitalmars-d-learn]

What's the best way to check if an (optional) argument has been 
passed?  One way is to use a default value, but I wonder if there 
is a tidier approach

Thanks.
(For startDate and endDate below)

struct NanoClientOptions
{
        string nanoUrl="tcp://127.0.0.1:9999";
        string[] tickers;
        DateTime startDate=DateTime(1,1,1);
        DateTime endDate=DateTime(9999,1,1);
}

auto helpInformation = getopt(
    args,
    "nanoUrl",  "Address of kaleidic data nanoserver eg 
tcp://127.0.0.1:9999",	&options.nanoUrl,
	    std.getopt.config.required,	"ticker|t", 	"Tickers to 
download data for",	&options.tickers,
            "startDate|s", "Start Date",                                    
&options.startDate,
            "endDate|e",       "End Date",                                  
&options.endDate
            );

Laeeth