Code sharing

One of the inconveniences of Xcode when we use it with large projects is that it doesn't allow reusing elements of the projects other than the build settings through .xcconfig files. Being able to reuse project definitions is useful for the following reasons:

• It eases the maintenance because changes can be applied in one place and all the projects get the changes automatically.
• It makes it possible to define conventions that new projects can conform to.
• Projects are more consistent and therefore the likelihood of broken builds due inconsistencies is significantly less.
• Adding a new projects becomes an easy task because we can reuse the existing logic.

Reusing code across manifest files is possible in Tuist thanks to the concept of project description helpers.

A TUIST UNIQUE ASSET

Many organizations like Tuist because they see in project description helpers a platform for platform teams to codify their own conventions and come up with their own language for describing their projects. For example, YAML-based project generators have to come up with their own YAML-based propietary templating solution, or force organizations onto building their tools upon.

Project description helpers

Project description helpers are Swift files that get compiled into a module, ProjectDescriptionHelpers, that manifest files can import. The module is compiled by gathering all the files in the Tuist/ProjectDescriptionHelpers directory.

You can import them into your manifest file by adding an import statement at the top of the file:

// Project.swift
import ProjectDescription
import ProjectDescriptionHelpers

ProjectDescriptionHelpers are available in the following manifests:

• Project.swift
• Package.swift (only behind the #TUIST compiler flag)
• Workspace.swift

Example

The snippets below contain an example of how we extend the Project model to add static constructors and how we use them from a Project.swift file:

Tuist/Project+Templates.swift

import ProjectDescription

extension Project {
  public static func featureFramework(name: String, dependencies: [TargetDependency] = []) -> Project {
    return Project(
        name: name,
        targets: [
            .target(
                name: name,
                destinations: .iOS,
                product: .framework,
                bundleId: "io.tuist.\(name)",
                infoPlist: "\(name).plist",
                sources: ["Sources/\(name)/**"],
                resources: ["Resources/\(name)/**",],
                dependencies: dependencies
            ),
            .target(
                name: "\(name)Tests",
                destinations: .iOS,
                product: .unitTests,
                bundleId: "io.tuist.\(name)Tests",
                infoPlist: "\(name)Tests.plist",
                sources: ["Sources/\(name)Tests/**"],
                resources: ["Resources/\(name)Tests/**",],
                dependencies: [.target(name: name)]
            )
        ]
    )
  }
}

Project.swift

import ProjectDescription
import ProjectDescriptionHelpers

let project = Project.featureFramework(name: "MyFeature")

A TOOL TO ESTABLISH CONVENTIONS

Note how through the function we are defining conventions about the name of the targets, the bundle identifier, and the folders structure.