Although I’m sure this won’t be super useful, I did find a use case for it yesterday while writing a command line log parsing tool in Groovy. One of the options I was providing users of this tool (mainly me) is the ability to pass in a comma-delimited list of files to process. Because of this I get a String that I can use split() against, and have a Collection to work with. I also provided a way to parse files that match a regular expression, so basically there are two ways to specify files.

Because of this the parser class is expecting a Collection of File objects. So then I was on task to find the best, or maybe just coolest, way to convert that Collection of Strings into a Collection of File objects.

For the first pass at this I use a simple each iteration like so:

def pretendCommandLineArg = "/home/psykoprogrammer/Documents/test.xls,/home/psykoprogrammer/Documents/ClearConnectUserGuide.docx"
def fileList = []

pretendCommandLineArg.split(",").each {
	fileList << new File(it)
}

fileList.each {
	println "File Name: ${it.getName()}, Path: ${it.getCanonicalPath()}"
}

And that worked just fine. Then it occured to me that I could add a metaClass enhancement to my already growing list of metaClass enhancements that can convert a string to a File object. That’s simple enough to do.

String.metaClass.toFile { basePath = "" ->
	new File("${basePath}${delegate}")
}

With that enhancement to the String class I can now do something like this:

"/home/adampresley/filea.txt".toFile()
"filea.txt".toFile("/home/adampresley/")

That’s pretty neat, but what about the fact I have a command line argument with a list of files delimited by a comma? Simple.

def pretendCommandLineArg = "/home/adampresley/test.xls,/home/adampresley/testfile.txt"
def fileList = pretendCommandLineArg.split(",")*.toFile()

fileList.each {
	println "File Name: ${it.getName()}, Path: ${it.getCanonicalPath()}"
}

By using the spread operator I can apply my new toFile() String method to each String in the Collection! Pretty cool eh? Although not the most useful thing hopefully this gets your brain pumping on the coolness that is Groovy! Happy coding!