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3.1 Motoko package managers

Intermediate
Tutorial

Mops is a package manager for Motoko. In this guide, you'll explore how to download and install Mops, then how to import and use different libraries through it.

What is a package manager?​

A package manager is a collection of tools that automates installing, upgrading, configuring, and removing software packages or libraries. They help efficiently manage the dependencies of a project. Mops and Vessel are two package managers for Motoko. Mops supports over 100 libraries for Motoko, spanning several different functionalities such as utility, encoding, cryptography, data structure libraries, and more.

Using Mops with ICP Ninja​

ICP Ninja supports adding Mops packages to projects. For example, open the Flying Ninja project and view the mops.toml file to see the packages used within the project:

# Motoko dependencies (https://mops.one/)

[dependencies]
base = "0.14.1"

Simply edit this file with any Mops packages you'd like to use within your project. For example:

time = "1.0.7"

In the project's dfx.json file, you will see Mops configured as the package manager through the following line:

dfx.json
...
{
  "defaults": {
    "build": {
      "packtool": "mops sources"
    }
  }
}
...

Using Mops in a local environment​

To install Mops, first be sure to have set up your developer environment and installed the IC SDK and Node.js, as described in the previous module, 0.3: Developer environment setup. Mops is supported in dfx versions 0.10.0 and higher.

Then, to install Mops, run the command:

npm i -g ic-mops

Create a new project in your working directory. Open a terminal window, navigate into your working directory (developer_liftoff), then use the following commands to start dfx and create a new project:

dfx start --clean --background
dfx new mops_example --type=motoko --no-frontend
cd mops_example

Configuring your local project to use Mops​

Then, open the dfx.json file within your project. Add Mops as a packtool in the file by adding the following line:

dfx.json
{
  "defaults": {
    "build": {
      "packtool": "mops sources"
    }
  }
}

Initializing Mops​

Then, initialize the Mops configuration with the command:

mops init

You'll be prompted to choose whether you plan to use Mops to pull packages or publish packages:

? Select type: › - Use arrow-keys. Return to submit.
❯   Project (I just want to use mops packages in my project)
    Package (I plan to publish this package on mops)

In this case, select 'Project.' For more information about publishing packages, see the publishing a package section.

You will also be prompted to choose if you'd like to use a GitHub workflow. This is optional.

Adding packages to mops.toml.​

To install a package with Mops, you need to specify the package in the mops.toml file within your project. To add a package to this file, you can use the command maps add and then the package name:

mops add base

Or, you can add packages directly from GitHub by specifying the repository's URL:

mops add https://github.com/dfinity/motoko-base

You can also specify the branch, commit hash, or tag by adding #<branch/tag/hash>:

mops add https://github.com/dfinity/motoko-base#moc-0.9.1

If you have a locally stored package, you can put the source files inside your project's directory and then add them by specifying the path:

mops add ./local-package

Using any of these workflows will add the package to the mops.toml file.

Then, to install all packages specified in this file, use the command:

mops install

Publishing a package​

If you develop a package that you'd like to publish so other developers can use it, you can publish it to the Mops registry! For instructions on publishing a package to Mops, check out the Mops documentation.

Importing packages into your Motoko code​

Once a package has been installed, you can import it into your Motoko code file using the line import PackageName "mo:<package_name>";, such as:

src/character_count/main.mo
import Text "mo:base/Text";
import Bool "mo:base/Bool";

actor characterCount {

    public func test(text: Text) : async Bool {
        let size = Text.size(text);
        return size % 2 == 0;
    };
};
ICP AstronautNeed help?

Did you get stuck somewhere in this tutorial, or do you feel like you need additional help understanding some of the concepts? The ICP community has several resources available for developers, like working groups and bootcamps, along with our Discord community, forum, and events such as hackathons. Here are a few to check out: