Object Tutorials Chapter 4 #1848

lxfind · 2022-05-06T18:37:55Z

This PR adds Chapter 4, object wrapping.
The last section is still work in progress, but want to send this out early to get feedback.

sblackshear

Super helpful stuff!

doc/src/build/programming-with-objects/ch4-object-wrapping.md

sblackshear · 2022-05-08T01:03:35Z

doc/src/build/programming-with-objects/ch4-object-wrapping.md

+
+Now let's look at how we could enable a swap/trade between your object and others' objects. A straightforward idea is this: define a function that takes two objects from two accounts, and swap their ownership. But this doesn't work in Sui! Recall from Chapter 2 that only object owners can send a transaction to mutate the object. So one person cannot send a transaction that would swap their own object with someone else's object.
+
+In the future, we will likely introduce multi-sig transactions so that two people can sign the same transaction for this type of usecase. However you may not always be able to find someone to swap with right away. A multi-sig transaction won't work in this scenario. Even if you can, you may not want to carry the burden of finding a swap target.


"Multi-sig" usually refers to requiring multiple keys to send a tx from a single address rather than sending a tx that acts on behalf of multiple addresses. We used to call the idea you are describing "multi-agent" transactions.

doc/src/build/programming-with-objects/ch4-object-wrapping.md

kchalkias · 2022-05-08T01:28:49Z

doc/src/build/programming-with-objects/ch4-object-wrapping.md

+}
+```
+Now `Bar` is also a Sui object type. When we put a Sui object of type `Bar` into a Sui object of type `Foo`, the Sui object of type `Bar` is said to be **wrapped**.
+There are some interesting consequences of wrapping an Sui object into another. When an object is wrapped, this object no longer exists independently on-chain. One will no longer be able to look up this object by its ID. This object becomes part of the data of the object that wraps it. Most importantly, one can no longer pass the wrapped object as an argument in any way in Move calls. The only access point is through the wrapping object.


We should probably explain 3 edge cases (with a note):

It's not clear if we can wrap an already wrapped object?
wrap(wrap(wrap(obj)))

Are accidental cycles resolved automatically at compilation or the dev should take care of it?

Can a regular struct hold a Sui object (thus the opposite from the example)?

Good call! Will explain them in the doc.
To answer your question

No. A wrapped object cannot be used directly.

Since 1) is no, there cannot be cycles

No.

Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Replace One with We Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Introduce Wrapper object Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Fix typo, remove hyphens from third-party nouns Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Refine service operator limitations Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Specify old sword returned Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

lxfind · 2022-05-09T16:44:41Z

Thank you @Clay-Mysten!
I will also update based on Kostas's question latter today.

Make initial edits

kchalkias · 2022-05-09T23:30:14Z

doc/src/build/programming-with-objects/ch4-object-wrapping.md

+
+There are some interesting consequences of wrapping an Sui object into another. When an object is wrapped, this object no longer exists independently on-chain. We will no longer be able to look up this object by its ID. This object becomes part of the data of the object that wraps it. Most importantly, *we can no longer pass the wrapped object as an argument in any way in Move calls*. The only access point is through the wrapping object.
+
+>:bulb: The fact that you can no longer use a wrapped Sui object means that it's impossible to create circular wrapping behavior, where A wraps B, B wraps C, and C also wraps A.


kchalkias · 2022-05-09T23:31:01Z

doc/src/build/programming-with-objects/ch4-object-wrapping.md

+    value: u64,
+}
+```
+> :book: For a struct type to be capable of being embedded in a Sui object struct (which will have `key` ability), the embedded struct type must have the `store` ability.


Finish direct edits

Clay-Mysten

Hi Xun,

Fantastic work, as always. I made my edits directly in two commits and have no questions or TODOs. I did note you and I had commits going simultaneously where you were addressing feedback from Kostas.

Please, please help me ensure I overwrote none of your work. I saw no conflicts but don't yet know how they would manifest in GitHub at the commit (as opposed to PR) level. If I can help, let me know. Thanks!

* Object Tutorials Chapter 4 * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Replace One with We Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Introduce Wrapper object Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Fix typo, remove hyphens from third-party nouns Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Refine service operator limitations Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Update doc/src/build/programming-with-objects/ch4-object-wrapping.md Specify old sword returned Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com> * Address Kostas's questions * Create ch4-object-wrapping.md Make initial edits * Update ch4-object-wrapping.md Finish direct edits Co-authored-by: Clay-Mysten <100217682+Clay-Mysten@users.noreply.github.com> Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Object Tutorials Chapter 4

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lxfind requested review from awelc, sblackshear, damirka and todd-mystenlabs May 6, 2022 18:37

lxfind requested a review from Clay-Mysten as a code owner May 6, 2022 18:37

github-actions bot added the Type: Documentation Improvements or additions to documentation label May 6, 2022

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Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

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Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

dc828d8

Replace One with We Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

3b42d3e

Introduce Wrapper object Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

21167a7

Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

3cdcad2

Fix typo, remove hyphens from third-party nouns Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

394f613

Fix typo Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

984b2fb

Refine service operator limitations Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

Update doc/src/build/programming-with-objects/ch4-object-wrapping.md

687b593

Specify old sword returned Co-authored-by: Sam Blackshear <sam.blackshear@gmail.com>

lxfind force-pushed the chapter-4 branch from a8d4a46 to 0b6eeb1 Compare May 9, 2022 23:10

Address Kostas's questions

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lxfind merged commit 254ab75 into main May 10, 2022

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Object Tutorials Chapter 4 #1848

Object Tutorials Chapter 4 #1848

lxfind commented May 6, 2022

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kchalkias May 8, 2022 •

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lxfind commented May 9, 2022

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		Now let's look at how we could enable a swap/trade between your object and others' objects. A straightforward idea is this: define a function that takes two objects from two accounts, and swap their ownership. But this doesn't work in Sui! Recall from Chapter 2 that only object owners can send a transaction to mutate the object. So one person cannot send a transaction that would swap their own object with someone else's object.

		In the future, we will likely introduce multi-sig transactions so that two people can sign the same transaction for this type of usecase. However you may not always be able to find someone to swap with right away. A multi-sig transaction won't work in this scenario. Even if you can, you may not want to carry the burden of finding a swap target.


		There are some interesting consequences of wrapping an Sui object into another. When an object is wrapped, this object no longer exists independently on-chain. We will no longer be able to look up this object by its ID. This object becomes part of the data of the object that wraps it. Most importantly, we can no longer pass the wrapped object as an argument in any way in Move calls. The only access point is through the wrapping object.

		>:bulb: The fact that you can no longer use a wrapped Sui object means that it's impossible to create circular wrapping behavior, where A wraps B, B wraps C, and C also wraps A.

Object Tutorials Chapter 4 #1848

Object Tutorials Chapter 4 #1848

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