Groovy: v 1.0

groovy.html.markdown

@@ -2,7 +2,7 @@
 language: Groovy
 filename: learngroovy.groovy
 contributors:
-    - ["Roberto Perez Alcolea", "http://github.com/rpalcolea"]
+    - ["Roberto Pérez Alcolea", "http://github.com/rpalcolea"]
 filename: learngroovy.groovy
 ---
 
@@ -182,6 +182,179 @@ for ( e in map ) {
     x += e.value
 }
 
+/*
+  Operators
+
+  Operator Overloading for a list of the common operators that Groovy supports: http://groovy.codehaus.org/Operator+Overloading
+
+  Helpful groovy operators
+*/
+//Spread operator:  invoke an action on all items of an aggregate object.
+def technologies = ['Groovy','Grails','Gradle']
+technologies*.toUpperCase() //equivalent to: technologies.collect { it?.toUpperCase() }
+
+//Safe navigation operator: used to avoid a NullPointerException.
+def user = User.get(1)
+def username = user?.username
+
+
+/*
+  Closures
+  A Groovy Closure is like a "code block" or a method pointer. It is a piece of code that is defined and then executed at a later point.
+
+  More info at: http://groovy.codehaus.org/Closures+-+Formal+Definition
+*/
+//Example:
+def clos = { println "Hello World!" }
+
+println "Executing the Closure:"
+clos()
+
+//Passing parameters to a closure
+def sum = { a, b -> println a+b }
+sum(2,4)
+
+//Closures may refer to variables not listed in their parameter list.
+def x = 5
+def multiplyBy = { num -> num * x }
+println multiplyBy(10)
+
+//If you have a Closure that takes a single argument, you may omit the parameter definition of the Closure
+def clos = { print it }
+clos( "hi" )
+
+/*
+  Groovy can memorize closure results:
+  More info at:
+            http://roshandawrani.wordpress.com/2010/10/18/groovy-new-feature-closures-can-now-memorize-their-results/
+            http://www.solutionsiq.com/resources/agileiq-blog/bid/72880/Programming-with-Groovy-Trampoline-and-Memoize
+            http://mrhaki.blogspot.mx/2011/05/groovy-goodness-cache-closure-results.html
+/*
+def cl = {a, b ->
+    sleep(3000) // simulate some time consuming processing
+    a + b
+}
+
+mem = cl.memoize()
+
+def callClosure(a, b) {
+    def start = System.currentTimeMillis()
+    mem(a, b)
+    println "Inputs(a = $a, b = $b) - took ${System.currentTimeMillis() - start} msecs."
+}
+
+callClosure(1, 2)
+callClosure(1, 2)
+callClosure(2, 3)
+callClosure(2, 3)
+callClosure(3, 4)
+callClosure(3, 4)
+callClosure(1, 2)
+callClosure(2, 3)
+callClosure(3, 4)
+
+/*
+  Expando
+
+  The Expando class is a dynamic bean so we can add properties and we can add closures as methods to an instance of this class
+
+  Reference: http://mrhaki.blogspot.mx/2009/10/groovy-goodness-expando-as-dynamic-bean.html
+*/
+  def user = new Expando(name:"Roberto")
+  assert 'Roberto' == user.name
+
+  user.lastName = 'Pérez'
+  assert 'Pérez' == user.lastName
+
+  user.showInfo = { out ->
+      out << "Name: $name"
+      out << ", Last name: $lastName"
+  }
+
+  def sw = new StringWriter()
+  println user.showInfo(sw)
+
+
+/*
+  Metaprogramming (MOP)
+*/
+
+//Using ExpandoMetaClass to add behaviour
+String.metaClass.testAdd = {
+    println "we added this"
+}
+
+String x = "test"
+x?.testAdd()
+
+//Intercepting method calls
+class Test implements GroovyInterceptable {
+    def sum(Integer x, Integer y) { x + y }
+
+    def invokeMethod(String name, args) {
+        System.out.println "Invoke method $name with args: $args"
+    }
+}
+
+def test = new Test()
+test?.sum(2,3)
+test?.multiply(2,3)
+
+//Groovy supports propertyMissing for dealing with property resolution attempts.
+class Foo {
+   def propertyMissing(String name) { name }
+}
+def f = new Foo()
+
+assertEquals "boo", f.boo
+
+/*
+  TypeChecked and CompileStatic
+  Groovy, by nature, is and will always be a dynamic language but it supports typechecked and compilestatic
+
+  More info: http://www.infoq.com/articles/new-groovy-20
+*/
+//TypeChecked
+import groovy.transform.TypeChecked
+
+void testMethod() {}
+
+@TypeChecked
+void test() {
+    testMeethod()
+
+    def name = "Roberto"
+
+    println naameee
+
+}
+
+//Another example:
+import groovy.transform.TypeChecked
+
+@TypeChecked
+Integer test() {
+    Integer num = "1"
+
+    Integer[] numbers = [1,2,3,4]
+
+    Date date = numbers[1]
+
+    return "Test"
+
+}
+
+//CompileStatic example:
+import groovy.transform.CompileStatic
+
+@CompileStatic
+int sum(int x, int y) {
+    x + y
+}
+
+assert sum(2,5) == 7
+
+
 ```
 
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