I made a cake for Tom. I made a cake for Tom. I bought a bag for my mother. I bought a bag for my mother.
I think English is easy. I think she is an angel. Distinguish between the two structures: I made John our chairman. I made a cake for John. The method is simple: add a be verb after the object, which is a complement if it can form a complete sentence. For example, we can say that John is our chairman. So the chairman of our last sentence is an object complement, which can't form a complete sentence, so it is a direct object. For example, we can't say: John is a cake. So the cake is the direct object.
The subject-predicate double object structure is subject+predicate+direct object+indirect object. For example, my father will buy me a walkman, and the subject-predicate object complement is subject+predicate+object+object complement. For example, leave me alone.
Subject-predicate double object, there is no connection between the two objects, but subject-predicate object complement, object and object complement can form a complete sentence, like the one upstairs. There is no connection between me and a book. Room and warmth can form the sentence "The room is warm". The general format of double objects is sb. +something. The general format of object and object complement is sb. /sth+adv/adj/ incomplete sentence structure, etc.