Question

In the following Groovy code snipped to add a fileAsString method to the String class, could someone explain what exactly ‘this’ refers to. I thought it was the object on which the fileAsString method is invoked, but apparently that’s actually what delegate refers to.

String.metaClass.fileAsString = {     this.class.getResourceAsStream(delegate).getText() } 

Thanks, Don

Answer 1

The newly defined method is a closure, so ‘this’ will have the same meaning as it does when the method is defined. Usually ‘this’ will refer to the object that defined the method, like below:

class Foo {     def meta() {         String.metaClass.bar = {             println(this.class)   // 'this' refers to the instance of Foo         }     }      def main() {         meta()         new String().bar()     } } new Foo().main()                  // prints 'class Foo'