How to change object reference inside another object in Scala?

Question

I have a situation where some objects come from an external Jar. There is an object X used from other objects like this:

object X {
    def foo() = ....
... more methods to follow
}

object A {
    def bar() = X.foo()
    ...few more methods using X
}

object B {
    def baz() = X.baz()
     ...few more methods using X
}

...other objects using X...

All that objects belong to the same Jar package and I need to use the classes A,B,etc but with a different reference than X (would be my local X). Is there a way to replace somehow X inside my project that is using a jar defined in that way?

Yeah, I supposed that. I just was ranting because you are now in a big problem because someone didn't design their code correctly. Why do you need to replace X? — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Apr 22, 2020 at 13:26
I have to inject different cloud configurations that "wrap" Spark processes and the code is meant to run on a "physical" env only. — Randomize
– Randomize, Commented Apr 22, 2020 at 13:38

Ivan Stanislavciuc · Accepted Answer · 2020-04-22 10:33:26Z

1

In short, no.

In long, it is possible but it's more like a hack rather than a proper solution.

You can redefine X within the same package name as original X and then rely on classloader order of jars to load your X first.

The correct solution is a redesign of your program so it allows "injection" of implementations. For example in this way

trait X {
    def foo() = ....
... more methods to follow
}

object X extends X
object Y extends X

object A {
    def bar(x: X) = x.foo()
    ...few more methods using X
}

object B {
    def baz(x: X) = x.baz()
     ...few more methods using X
}

answered Apr 22, 2020 at 10:33

Ivan Stanislavciuc

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1 Comment

Randomize Over a year ago

It is not my program, I mean I cannot change it (so not redesign it)

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