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Comment by function_seven | Hacker News Reader

I don't think it's about sending a message into the void and "hoping" that a compatible agent receives the message.

Rather, it's about your object not having to know who is handling the message, only what the message is ("what" in both content and type).

It's still up to you as the programmer to make sure that you have implemented the other objects to act on whatever message types your code will pass. Just like it's up to you to make sure the method exists in the target class when the caller tries to invoke it.

Later on, if you decide to swap out your logging infrastructure for a different one, you don't need to update all the places that called the old one. You just tell your new logger to listen for messages directed at Logger.

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> I don't think it's about sending a message into the void and "hoping" that a compatible agent receives the message.

Except that is the bacterial model. When you want something done, you signal for it by releasing proteins, and keep releasing proteins until you're satisfied even if the work ended up being done 50 times more than you needed. That's why biological systems so commonly overreact to stimulus. The biological method is to flood communication until whatever demanded response is met. It's the equivalent of a user mashing a button until a program responds, like the elevator button problem.

Actually, elevators seem like an extremely good analogy for this kind of asynchronous service system.

I understand we're not trying to perfectly mimic the analogy, but I think it's important to see that nature's model, while robust and asynchronous, carries significant problems due to how it communicates. It's that very robustness that we're trying to mimic, so we should expect to inherit some of the problems that go along with it.

Great insight! To add to this: To counteract, one needs to implement some kind of synchronization device, which has bring plenty of other problems. It would be exiting if nature would choose a more snychronized approach if it had the choice.

Yeah, the biological model is much more messy. I think we can take some lessons from it while still enforcing a "God Mode" on our local machine, ensuring that a compatible process is always running to receive the message.

Though, as GP stated earlier, this does make some more sense from a distributed networking perspective, where no machine has control over the existence of its peers. In that case, having a setup where the message is sent out on a service bus to be snatched up by a compatible listener is closer to the biological analogy.

But is it possible for the compiler to check that some object was actually set to wait to receive a particular message that another object was instructed to send? When coding with method calls, it is possible to accidentally leave a stub instead of method code that is supposed to produce some important side effect, say, but at least you know where to look.

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