Awesomeness of groovy named parameters

Friday, 13 January 2012

Awesomeness of groovy named parameters

Posted by Grisha Mykhalyuno , at 10:27

How do you call typical method with few parameters. Lets assume we have method that sends email with signature

send(String from, String to, String subject, String body) {
  println "sender ${from}"
  println "sender ${to}"
  println "sender ${subject}"
  println "sender ${body}"
}

typical java call would be

send("john@example.com", "mike@example.com", "greetings", "Hello Goodbye")

Too many strings, don't you think? I have to check java docs all the time I'm writing this method.
Groovy allows us to pass parameters as map without []. If we pass map into method groovy set it to the first parameter. Let's look into other example

send from:"john@example.com",
     to:"mike@example.com",
     subject:"greetings",
     body:"Hello Goodbye"

Much more readable as for me. And method will looks like

send(params) {
  println "sender ${params.from}"
  println "sender ${params.to}"
  println "sender ${params.subject}"
  println "sender ${params.body}"
}

5 comments to “Awesomeness of groovy named parameters”

13 January 2012 19:01

Orest Ivasiv says:

Yes, it's a pain in Java, named parameters it's cool feature.

But, there are several solation how to solve this issue:

1)
String from, to, subject, body;
send(from="john@example.com", to="mike@example.com", subject="greetings", body="Hello Goodbye")

2) use map
send(new HashMap {{
put("from", "john@example.com");
put("to", "mike@example.com");
put("subject", "greetings");
put("body", "Hello Goodbye");}}) {
...
}

3) Implement Fluent API
Mail.from("john@example.com").to("mike@example.com").subject("greetings").body("Hello Goodbye").send();

I prefer 2) and 3)

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13 January 2012 19:07

Grygoriy Mykhalyunyo says:

#3 (Builder) is the first choice for me, really love it. I think I will write about groovy builder soon.

But I think we can find way to write in DSL style in all languages, unfortunately most devs still prefer usign tons of params

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13 January 2012 19:10

Grygoriy Mykhalyunyo says:

Maybe I was not really fair when didn't mention builder in original post. Will try to fix this in future

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13 January 2012 21:21

Oleksandr Pavlyshak says:

With named parameters you get the advantage of compiler checks.
I doubt there is any simple way to make sure at compile time that the Builder was supplied with all the required params. And by simple way I mean going without tons of builder-specific interfaces.

Love Builder though, when it comes to anything more complex than passing parameters.

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22 May 2013 06:11

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