Scala's "Pimp My Library" Pattern example
I always find myself wanting to find a quick example of this to show people. Essentially, the "Pimp My Library" pattern allows you to decorate classes with additional methods and properties. The following is how you would add a method "bling" to java.lang.String which will add asterisks to either end:
class BlingString(string: String) {
def bling = "*" + string + "*"
}
implicit def blingYoString(string: String) = new BlingString(string)This defines a class BlingString with the bling method, and then uses an implicit definition to "teach" Scala how to convert from a java.lang.String to the new type. You can then call the method on any java.lang.String object, as long as the implicit is defined in the same scope:
scala> "Let's get blinged out!".bling
res0: java.lang.String = *Let's get blinged out!*Written by Ben Burton
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5 Responses
I came here courtesy of google, looking for what pimping means in the Scalasphere, thanks! Well, with power comes some responsibility..... but isn't there a syntactically simpler way to add behavior to a type? this is soooo cumbersome and blingYoString is a name you'd never use in your code again, so it feels like it should have rather been anonymous. What do you think?
Recommended syntax for this is to use an implicit value class to avoid runtime creation of a wrapper class: http://docs.scala-lang.org/overviews/core/value-classes.html
implicit class BlingString(string: String) extends AnyVal {
def bling = "*" + string + "*"
}
Thanks eranation, that's much cleaner!
Short, sweet & concise
simple concise and understandable
