whose object are "you"?

Question

A Cambridge Dictionary post says

We use all of before personal pronouns (us, them), demonstrative pronouns (this, that, these, those) and relative pronouns (whom, which). The personal pronoun is in the object form:

I need to speak to all of you for a few minutes.

...

I used to have three pens but I’ve lost all of them.

whose object are "you" in this case? How about "them"?

I am aware the concept of object,

a noun or noun phrase that is affected by the action of a verb or that follows a preposition

In the sentence "I like ice cream", "ice cream" is the object of the verb "like".

I also aware that "you", as a pronoun, could play a role of object. In the sentence "Alice likes you", "you" is the object of the verb "like".

question

I don't understand whose object are "you" and "them" in first two examples. I don't understand the term "object form" either. Could someone please give a hint?

Answer 1

It isn't a grammatical direct object. It is "in object form".

Personal pronouns are unlike other words because some have different forms for object and subject. The object form of I is me.

I hit Jane. Jane hit me.

But "you" doesn't have a different object form

You hit Jane. Jane hit you.

The object form is also used for words that are not direct objects, but may be indirect objects. It is also used for exclamations

Joe put the hat on me.

"Who wants an ice cream?" -- "Me!"

By analogy with verbal objects, prepositions also have objects. In a prepositional phrase "on me", me is the object of preposition "on".

In you examples:

I need to speak to all of you.

the phrase "all of you" is an indirect object of the infinitive verb speak (alternatively you can consider it an indirect object of the verb phrase "need to speak"). You can consider "you" to be the object of the preposition "of"

He bought gifts for all of us.

"all of us" is an indirect object of bought.