Dash (--) and Comma (,)

[Kenneth]

My father--David, is a doctor.
My father--David is a doctor.
My father, David, is a doctor.
My father--David--is a doctor.

Which of the above is correct? And would anyone please explain the usage for dash and comma as in structures similar to the above?

Thanks in advance.

Regards,
Kenneth

[Casiopea]

My father--David, is a doctor.
My father--David is a doctor.
My father, David, is a doctor.
My father--David--is a doctor.

Which of the above is correct? And would anyone please explain the usage for dash and comma as in structures similar to the above?

Thanks in advance.

Regards,
Kenneth

Use a dash if the information adds extra knowledge that's not directly related to the flow of the sentence. For example, "David" renames the subject "My father", which makes it directly related to the flow of the sentence:

My father, David, is a doctor.

[Kenneth]

Thanks Casiopea. But what about the following (I'm still not very sure about the usage of (--):

1. Just then, Kylie—who was heading out of the classroom—passed by the boys and was waving them goodbye.

or

Just then, Kylie—heading out of the classroom—passed by the boys and was waving them goodbye.



2. Lionel said to Tham—whose seat was next to his—as he quickly stuffed all his belongings into the schoolbag.


3. “All right” came straight from Invincible—Lionel’s screen name.

4. The last time she entered—as he could recall—she broke down right away.

[Kenneth]

Can anyone please help?

[Casiopea]

Can anyone please help?

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