This section details how to go about using the dynamic features of Groovy such as implementing the GroovyObject interface and using ExpandoMetaClass, a expandable MetaClass that allows adding of methods, properties and constructors.
- Using invokeMethod and getProperty
- Using methodMissing and propertyMissing
- Evaluating the MetaClass runtime
- Using ExpandoMetaClass to add behaviour
- Customizing MetaClass for a single instance
Dynamic Method Invocation
You can invoke a method even if you don't know the method name until it is invoked:
class Dog {
def bark() { println "woof!" }
def sit() { println "(sitting)" }
def jump() { println "boing!" }
}
def doAction( animal, action ) {
animal."$action"() //action name is passed at invocation
}
def rex = new Dog()
doAction( rex, "bark" ) //prints 'woof!'
doAction( rex, "jump" ) //prints 'boing!'
You can also "spread" the arguments in a method call, when you have a list of arguments:
def max(int i1, int i2) { Math.max(i1, i2) } def numbers = [1, 2] assert max( *numbers ) == 2
This also works in combination of the invocation with a GString:
someObject."$methodName"(*args)
