Question

In Groovy everything is Object, even numbers

assert 1.getClass() == Integer

In Groovy you can override existing method in an existing class in runtime

Integer.metaClass.or = { right -> println "$delegate or $right" }

Now we can call or operator on any number using pipe (|)

1.or("hello") // prints: 1 or hello
1 | "hello" // prints: 1 or hello

So far so good. Now let’s try to or an Integer with an Integer

2.or(3) // nothing happens
2 | 3 // nothing happens

This leads us to my questions:

• Why nothing happens?
• Is this an optimization bug?
• How to make it work for any type?

Answer 1

It’s probably choosing an already existing or method that takes an integer, rather than your more generic Object version.

Does it work if you do:

Integer.metaClass.or = { Integer right -> println "$delegate or $right" }

Not at a computer at the moment though, so can’t validate this :-/