Add Self to your list, which was even purer than Smalltalk since it got rid of the classes and let the objects stand by themselves.
It's not just the actor model, though. In the actor model, all the actors are contributors to the conversation. The subjects of conversation are something else. In object oriented programming, the subjects of conversation are the same category of things as the agents of conversation, and may move back and forth freely.
The simplest way to see the difference is to think about how a new contributor to the conversation is added. In the actor model, some actor forks a new actor in response to a message. If I have built up the state to describe a new actor, there is still a step to bring it to life that changes it from one thing to another.
In object oriented programming, when you build up that state, it may become a contributor to the conversation at any point in time and then go back to being a subject of conversation, or do both at once. There is no switch.
It's not just the actor model, though. In the actor model, all the actors are contributors to the conversation. The subjects of conversation are something else. In object oriented programming, the subjects of conversation are the same category of things as the agents of conversation, and may move back and forth freely.
The simplest way to see the difference is to think about how a new contributor to the conversation is added. In the actor model, some actor forks a new actor in response to a message. If I have built up the state to describe a new actor, there is still a step to bring it to life that changes it from one thing to another.
In object oriented programming, when you build up that state, it may become a contributor to the conversation at any point in time and then go back to being a subject of conversation, or do both at once. There is no switch.