llms.txt
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Package

Move is a language for writing smart contracts - programs that are stored and run on the blockchain. A single program is organized into a package. A package is published on the blockchain and is identified by an address. A published package can be interacted with by sending transactions calling its functions. It can also act as a dependency for other packages.

To create a new package, use the sui move new command. To learn more about the command, run sui move new --help.

A package consists of modules - separate scopes that contain functions, types, and other items.

package 0x...
    module a
        struct A1
        fun hello_world()
    module b
        struct B1
        fun hello_package()

Package Structure​

Locally, a package is a directory with a Move.toml file and a sources directory. The Move.toml file - called the "package manifest" - contains metadata about the package, and the sources directory contains the source code for the modules. A package usually looks like this:

sources/
    my_module.move
    another_module.move
    ...
tests/
    ...
examples/
    using_my_module.move
Move.toml

The tests directory is optional and contains tests for the package. Code placed into the tests directory is not published onchain and is only available in tests. The examples directory can be used for code examples, and is also not published onchain.

Published Package​

During development, a package doesn't have an address yet, and 0x0 is used in its place. Once a package is published, it gets a single unique address on the blockchain containing its modules' bytecode. A published package becomes immutable and can be interacted with by sending transactions.

0x...
    my_module: <bytecode>
    another_module: <bytecode>

While the published bytecode can never be changed, a package can be upgraded: an upgrade publishes a new version of the package at a new address, leaving the old version intact. We touch on the implications throughout the book: the Package Upgrades section explains the mechanics, and the Upgradeability Practices guide covers how to design for upgrades.

Further Reading​

llms.txt