is it possible to copy a `Random` instance? or do ...

# announcements

[christophsturm]

is it possible to copy a Random instance? or do i have to store the seed and create it from that again?

[Egor Trutenko]

Why would you want that?
a) Random is itself thread-safe, so you can call the same instance from any number of threads;
b) Creating a Random instance from seed is actually the same as copying an existing instance.

[Alan Evans]

b) if you've taken no values from it

[christophsturm]

i want to make my random values reproducable, and i want to do that by injecting a random instance instead of injecting the seed

[Alan Evans]

what do you use to inject?

[Alan Evans]

e.g. in Koin,

factory { Random(1234) }

Would always inject a random with same seed, 1234

[christophsturm]

i have this library that fills data classes with random data and i want to make the seed configurable. but i thought its nicer to inject the whole random generator instead of just the seed. https://github.com/christophsturm/randolf/blob/inject-random/src/test/kotlin/randolf/RandolfTest.kt#L196

[Alan Evans]

woah, how did I guess your seed?!

[Alan Evans]

ok, almost looks like you're doing your own DI and all you can cope with is singletons

[Alan Evans]

imagine this:

RandolfConfig(random = { Random(1234) })

That is, random is of type: () -> Random i.e. a factory. It creates a new random on demand.
Therefore, no actual Random instance exists on your config.

[Alan Evans]

Which is exactly how koin example works:```
factory { Random(1234) }
```

[christophsturm]

thats not what i want because that would not be random at all 🙂

[Alan Evans]

what?!

[christophsturm]

if i regenerate the random generator anytime i need a random i will always get the same number

[Alan Evans]

val oneTimeSeed = Random().next()
RandolfConfig(random = { Random(oneTimeSeed) })

[christophsturm]

right then i can just store the seed instead of the random in the config and thats also a fix

[Alan Evans]

yes, true

[christophsturm]

thanks for your thoughts!

[Alan Evans]

Random supports Serializable so if you really wanted to copy it, you can serialize and deserialize.

[ilya.gorbunov]

Random supports Serializable

not yet, if we're talking about Kotlin's Random

[christophsturm]

basically it boils down to this: things that are not immutable should have a copy constructor