https://github.com/sui-foundation/sui-move-intro-course/tree/main/unit-two/lessons

文档不太全，目前是个人理解，下方描述了一些需要理清的关键问题

1. 有key ability的struct被称为Sui object，其第一个成员id: UID是object的唯一标识符，链上存储与查找数据均使用UID。销毁struct并不会销毁UID（object本身）。创建object（UID）使用object::new，销毁object使用object::delete(id)。

2. wrapped：指的是一个object被存放在另一个object内部，这需要被存放的object有store ability。存放发生后，被存放object实际上会被隐藏（不再能用其UID检索到该object），只有wrapping object被销毁了才可以重新取出该object，该object的可见性就恢复了，且前后UID不会发生变化（即还是同一个object）

   https://docs.sui.io/concepts/object-ownership/wrapped

3. 文档中描述了许多种object，包括shared、**Address-owned，是否shared只影响谁可以使用这个object（读/写均只有owner可以进行）。**无论权限如何，某种类型的struct只能由定义它的module创建（create/pack）、销毁（destroy/unpack）或修改。

4. 没有key ability的类型是如何被处理的？相比于有key的有哪些限制？：不能被存储，只能在当次transaction中创建后也必须在本次transaction中被销毁

5. 在flash loan中见到了key, store, drop均无的struct，获得它以后必须在本次transaction中调用创建它的module内的函数来销毁它，这种pattern被称为Hot Potato（烫手山芋）。

6. 有drop ability的struct可在离开作用域后被自动销毁，不需要创建它的module显式unpack

7. UID和ID有何区别？

       /// An object ID. This is used to reference Sui Objects.
       /// This is *not* guaranteed to be globally unique--anyone can create an `ID` from a `UID` or
       /// from an object, and ID's can be freely copied and dropped.
       /// Here, the values are not globally unique because there can be multiple values of type `ID`
       /// with the same underlying bytes. For example, `object::id(&obj)` can be called as many times
       /// as you want for a given `obj`, and each `ID` value will be identical.
       struct ID has copy, drop, store {
           bytes: address
       }
   
       /// Globally unique IDs that define an object's ID in storage. Any Sui Object, that is a struct
       /// with the `key` ability, must have `id: UID` as its first field.
       /// These are globally unique in the sense that no two values of type `UID` are ever equal, in
       /// other words for any two values `id1: UID` and `id2: UID`, `id1` != `id2`.
       /// This is a privileged type that can only be derived from a `TxContext`.
       /// `UID` doesn't have the `drop` ability, so deleting a `UID` requires a call to `delete`.
       struct UID has store {
           id: ID,
       }
   

   https://github.com/MystenLabs/sui/blob/testnet-v1.16.1/crates/sui-framework/packages/sui-framework/sources/object.move

   //! Objects whose struct type has key ability represent Sui objects.
   //! They have unique IDs that should never be reused. This verifier makes
   //! sure that the id field of Sui objects never get leaked.
   //! Unpack is the only bytecode that could extract the id field out of
   //! a Sui object. From there, we track the flow of the value and make
   //! sure it can never get leaked outside of the function. There are four
   //! ways it can happen:
   //! 1. Returned
   //! 2. Written into a mutable reference
   //! 3. Added to a vector
   //! 4. Passed to a function cal::;
   

   https://github.com/MystenLabs/sui/blob/testnet-v1.16.1/sui-execution/latest/sui-verifier/src/id_leak_verifier.rs

8. transfer：只有定义该object的module可以调用sui::transfer::transfer；有store ability的object方可被其他module调用sui::transfer::public_transfer