Pears of Wisdom - Groovy Fundamentals

Page 1

High Level Groovy Concepts

TODO

Basic Syntax

System.out.println("Hello Groovy") ; is the same as,

println("Hello Groovy"); is the same as,

println("Hello Groovy") is the same as,

println "Hello Groovy"

Groovy will let you write Java-like syntax, but really only needs basic ruby-like syntax.

def : used to define variables

String Interpolation is done like this:

def greeting = "Hello, "

println "$greeting" + "Groovy"

Adding the { } characters tell string interpolation to apply to a whole expression or variable, like this:

def greeting = "Hello, "

def who = ["Groovy", "World"]

println "$greeting" + "${who[0]}"

Idiomatic Groovy uses double quotes for string interpolation only, otherwise use a single quote.

Looping

def greeting = "Hello, "

def who = ["Groovy", "World"]

for (name in who) {

println "$greeting" + "$name"

}

Ranges

def numbers = 1..10 : This creates a collection, it also works with things like letters and enums

println numbers.from : This equals 1

println numbers.to : This equals 10

Functions

def camelCaseName(val) {

"Sweet"

}

Note that the last line in the method is returned by default.

You can explicitly call return if you need multiple return points.

Closures

def myClosure = { println "A closure" }

The each method can accept a closure

Each has an implicit reference to the current item in the iteration, which is 'it', like this:

def who = ["Groovy", "World"]

who.each({ println it })

This will print Groovy, then World

If you have multiple iterators you can explicitly define the current iteration like this:

who.each({ name -> println name })

Dump & Inspect

You can print out a lot of information about an object by calling dump. This should provide you the object type, its inheritance hierarchy, as well as its members

There is also a method called inspect. Developers are expected to override inspect with useful information. If they haven't don that, it defaults to the toString() method for the object.

With

This is a helper method on objects called with. It accepts a closure and prevents you from having to continually re-type a variable name whose dot methods you are accessing, like this:

data.with {

println item

println thing

}

AS OPPOSED TO

println data.item

println data.thing

Groovy Truthfulness

Any not null value evaluates to true on a boolean comparison, like this:

if (!value)

AS OPPOSED TO

if (value == null)

Categories

TODO

Page 2

Some Basic Activities

def file = new File('../path/to/file.xml')

def slurper = new XmlSlurper()

def data = slurper.parse(file)

println data.elementName

println data.@attribute

println data.elementA.elementB

println data.elementA.elementB.@otherAttr

XmlSlurper will also dynamically determine the type of XML object and try to convert it, so you can run collection methods on XML arrays, etc.