Using propertyMissing to enhance Date (in Groovy) at log4p

Using propertyMissing to enhance Date (in Groovy)

Published by peter December 2nd, 2007 in groovy.

In my previous post I had a go at dates and ranges in Groovy. I wasn't to enthusiastic about the fact that it felt a bit verbose and Java-ish. So I took the opportunity to have a go at the new meta-programming stuff in Groovy >= 1.1beta3.

Say I want to be able to do something like this (the properties being Calendar fields):

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GROOVY:

d = new Date()
println d.dayOfWeek
println d.hourOfDay
println "$d.hourOfDay:$d.minute"
etc...

For me, this seemed like a good case to implement using methodMissing and/or propertyMissing. I came up with the following:

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GROOVY:

Date.metaClass.propertyMissing = { String name ->
wrd = name[0].toUpperCase() + name[1..<name.size()] // dayOfWeek ==> DayOfWeek
split = wrd =~ /([A-Z][a-z]+)/ // collect words
par = split.collect{it}?.join('_').toUpperCase() // ["Day","Of","Week"] ==> DAY_OF_WEEK
try{
con = Calendar."$par" // see if the field exist in calendar, throws MissingPropertyException if not
Date.metaClass."get$wrd" <<{ // register the 'get' method ==> getDayOfWeek()
cal = Calendar.instance // obtain a Calendar instance
cal.time = delegate // set the time to the current instance
return cal.get(con) // get the field
}
}
catch(MissingPropertyException mpe){
throw new MissingPropertyException(name, delegate.class) // wrap the exception
}
delegate."get$wrd"()
}

Performance-wise (tips, anyone?) this might not be the best solution (the documentation is actually a bit scarce in this point) but now I can remove the dreaded calendar object from my previous code:

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GROOVY: