Swift Package Manager: Demystifying Targets and Libraries

Target vs Library

If you'v dabbled with Swift Package Manager (SwiftPM), you've likely encountered targets and libraries in a Package.swift file and wondered what sets them apart. These concepts are essential to structuring your code effectively, especially as projects grow larger.

In this post, we'll break down the difference between the two, explore how they're used, and walk through real-world examples that show how you can build scalable and modular Swift packages.

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What Exactly Is a Target?

In SwiftPM, a target is the fundamental unit of code compilation. It's basically a module that consists of source files, dependencies, and optionally resources or tests. Targets are used internally within your package.

For example:

.target(name: "Logger")

This line defines a module named Logger. You can import and use this module from other targets inside your package.

And a Library?

A library is a product. It’s what you offer to the outside world—other packages or apps that want to use your code. A library wraps one or more targets and makes them available for external use.

.library(name: "Logger", targets: ["Logger"])

This exposes the Logger target as a library, allowing developers to simply import Logger in their projects.

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Spotting the Differences

Concept	Target	Library
Function	Defines internal modules	Exposes modules to the outside world
Visibility	Only usable within the package	Public-facing for consumers
Contents	Code, tests, resources, dependencies	A collection of targets
Purpose	Organization and modularity	Distribution and consumption

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Practical Use Cases

One Target, Multiple Libraries

It’s possible to reuse the same target in more than one library. Here’s how that might look:

.target(name: "Logger")

.library(name: "BasicLogger", targets: ["Logger"])
.library(name: "AdvancedLogger", targets: ["Logger"])

Both BasicLogger and AdvancedLogger provide the same underlying functionality via the Logger target but can be packaged differently for different use cases.

A Library Made From Multiple Targets

You can also bundle multiple targets into one library. Let’s say you’ve broken your preferences logic into two targets:

.target(name: "Preferences")
.target(name: "Configs")

.library(name: "AppPreferences", targets: ["Preferences", "Configs"])

Now, users of your package can import AppPreferences and benefit from both underlying modules.

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Visual Representation

Here’s a simple diagram to help visualize both scenarios:

• On one side: Two targets (Preferences, Configs) feed into one library (AppPreferences).

• On the other: One target (Logger) is used by two different libraries (BasicLogger, AdvancedLogger).

1. One Library from Multiple Targets

Preferences ─┐

                           ├──▶ AppPreferences (Library)

Configs    ──┘

2. One Target Used in Multiple Libraries

                                       ┌────────▶ BasicLogger (Library)

Logger (Target) ───┤

                                       └────────▶ AdvancedLogger (Library)

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Analogy 💡

Think of it like this:

• target = class/module (internal building block)

• library = framework (exported to others)

You can have many targets (internal modules), and choose which ones to expose by wrapping them in libraries.

Wrapping Up

Knowing how to use targets and libraries effectively in SwiftPM helps you write cleaner, more modular code. Think of targets as your internal building blocks and libraries as the polished pieces you share with the world.

Getting comfortable with this structure makes managing large Swift codebases much easier and improves collaboration across modules. 

Tags: Swift, Swift Package Manager, Xcode, Libraries, Code Organization, iOS Development