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Write a Move Package

To begin, open a terminal or console at the location you plan to store your package. Use the sui move new command to create an empty Move package with the name my_first_package:

$ sui move new my_first_package

Running the previous command creates a directory with the name you provide (my_first_package in this case). The command populates the new directory with a skeleton Move project that consists of a sources directory and a Move.toml manifest file. Open the manifest with a text editor to review its contents:

my_first_package/Move.toml
[package]
name = "my_first_package"

# edition = "2024.alpha" # To use the Move 2024 edition, currently in alpha
# license = ""           # e.g., "MIT", "GPL", "Apache 2.0"
# authors = ["..."]      # e.g., ["Joe Smith (joesmith@noemail.com)", "John Snow (johnsnow@noemail.com)"]

[dependencies]
Sui = { git = "https://github.com/MystenLabs/sui.git", subdir = "crates/sui-framework/packages/sui-framework", rev = "framework/testnet" }

# For remote import, use the `{ git = "...", subdir = "...", rev = "..." }`.
# Revision can be a branch, a tag, and a commit hash.
# MyRemotePackage = { git = "https://some.remote/host.git", subdir = "remote/path", rev = "main" }

# For local dependencies use `local = path`. Path is relative to the package root
# Local = { local = "../path/to" }

# To resolve a version conflict and force a specific version for dependency
# override use `override = true`
# Override = { local = "../conflicting/version", override = true }

[addresses]
my_first_package = "0x0"

# Named addresses will be accessible in Move as `@name`. They're also exported:
# for example, `std = "0x1"` is exported by the Standard Library.
# alice = "0xA11CE"

[dev-dependencies]
# The dev-dependencies section allows overriding dependencies for `--test` and
# `--dev` modes. You can introduce test-only dependencies here.
# Local = { local = "../path/to/dev-build" }

[dev-addresses]
# The dev-addresses section allows overwriting named addresses for the `--test`
# and `--dev` modes.
# alice = "0xB0B"

The manifest file contents include available sections of the manifest and comments that provide additional information. In Move, you prepend the hash mark (#) to a line to denote a comment.

  • [package]: Contains metadata for the package. By default, the sui move new command populates only the name value of the metadata. In this case, the example passes my_first_package to the command, which becomes the name of the package. You can delete the first # of subsequent lines of the [package] section to provide values for the other available metadata fields.
  • [dependencies]: Lists the other packages that your package depends on to run. By default, the sui move new command lists the Sui package on GitHub (Testnet version) as the lone dependency.
  • [addresses]: Declares named addresses that your package uses. By default, the section includes the package you create with the sui move new command and an address of 0x0. The publish process replaces the 0x0 address with an actual on-chain address.
  • [dev-dependencies]: Includes only comments that describe the section.
  • [dev-addresses]: Includes only comments that describe the section.

Defining the package​

You have a package now but it doesn't do anything. To make your package useful, you must add logic contained in .move source files that define modules. Use a text editor or the command line to create your first package source file named my_module.move in the sources directory of the package:

$ touch my_first_package/sources/my_module.move

Populate the my_module.move file with the following code:

module my_first_package::my_module {

    // Part 1: Imports
    use sui::object::{Self, UID};
    use sui::transfer;
    use sui::tx_context::{Self, TxContext};

    // Part 2: Struct definitions
    struct Sword has key, store {
        id: UID,
        magic: u64,
        strength: u64,
    }

    struct Forge has key, store {
        id: UID,
        swords_created: u64,
    }

    // Part 3: Module initializer to be executed when this module is published
    fun init(ctx: &mut TxContext) {
        let admin = Forge {
            id: object::new(ctx),
            swords_created: 0,
        };
        // Transfer the forge object to the module/package publisher
        transfer::public_transfer(admin, tx_context::sender(ctx));
    }

    // Part 4: Accessors required to read the struct attributes
    public fun magic(self: &Sword): u64 {
        self.magic
    }

    public fun strength(self: &Sword): u64 {
        self.strength
    }

    public fun swords_created(self: &Forge): u64 {
        self.swords_created
    }

    // Part 5: Public/entry functions (introduced later in the tutorial)

    // Part 6: Private functions (if any)

}

The comments in the preceding code highlight different parts of a typical Move source file.

  • Part 1: Imports - Code reuse is a necessity in modern programming. Move supports this concept with imports that allow your module to use types and functions declared in other modules. In this example, the module imports from object, transfer, and tx_context modules. These modules are available to the package because the Move.toml file defines the Sui dependency (along with the sui named address) where they are defined.

  • Part 2: Struct declarations - Structs define types that a module can create or destroy. Struct definitions can include abilities provided with the has keyword. The structs in this example, for instance, have the key ability, which indicates that these structs are Sui objects that you can transfer between addresses. The store ability on the structs provides the ability to appear in other struct fields and be transferred freely.

  • Part 3: Module initializer - A special function that is invoked exactly once when the module publishes.

  • Part 4: Accessor functions - These functions allow the fields of the module's structs to be read from other modules.

After you save the file, you have a complete Move package.