Implementing Swift Package Manager –Example 2

Simple, Nested Static Libraries

In this example, the PackageConsumer utility simply consumes Package_BPrime, Version 1.0.0, which is a static library, that, in turn, consumes Package_A Version 1.0.0 (also a static library).

Here is the GitHub link to the PackageConsumer project Version 2.0.0. You can check out that version, and reproduce the results here.

Here is the source code for Package_BPrime, version 1.0.0:

import Foundation
import Package_A

public struct Package_BPrime: PackageProtocol {
    public let indent: Int
    public let text: String
    public init(indent inIndent: Int = 0) {
        indent = inIndent
        let prefix = String(repeating: "\t", count: inIndent)
        text =  "\(prefix)Package_BPrime, Version: 1.0.0\n" + Package_A(indent: inIndent + 1).text
    }
}

Here is the source for the Package_BPrime, Version 1.0.0 Package.swift file:

import PackageDescription

let package = Package(
    name: "Package_BPrime",
    platforms: [
        .iOS(.v11),
        .tvOS(.v11),
        .macOS(.v10_14),
        .watchOS(.v5)
    ],
    products: [
        .library(
            name: "Package-BPrime",
            targets: ["Package_BPrime"]),
    ],
    dependencies: [
        .package(name: "Package_A", url: "git@github.com:LittleGreenViper/SPMArticle-Package_A.git", from: "1.0.0")
    ],
    targets: [
        .target(
            name: "Package_BPrime",
            dependencies: [
                .product(name: "Package-A", package: "Package_A")
            ]
        ),
        .testTarget(
            name: "Package_BPrimeTests",
            dependencies: ["Package_BPrime"]
        ),
    ]
)

Here is the source code for Package_A, version 1.0.0:

import Foundation

public protocol PackageProtocol {
    var text: String { get }
    var indent: Int { get }
}

public struct Package_A: PackageProtocol {
    public let indent: Int
    public let text: String
    public init(indent inIndent: Int = 0) {
        indent = inIndent
        let prefix = String(repeating: "\t", count: inIndent)
        text =  "\(prefix)Package_A, Version: 1.0.0"
    }
}

And here is its Package.swift file:

import PackageDescription

let package = Package(
    name: "Package_A",
    platforms: [
        .iOS(.v11),
        .tvOS(.v11),
        .macOS(.v10_14),
        .watchOS(.v5)
    ],
    products: [
        .library(
            name: "Package-A",
            targets: ["Package_A"]),
    ],
    targets: [
        .target(
            name: "Package_A",
            dependencies: []),
        .testTarget(
            name: "Package_ATests",
            dependencies: ["Package_A"]),
    ]
)

Here is the source for the PackageConsumer Version 2.0.0 file:

import Foundation
import Package_BPrime

struct PackageConsumer {
    let text: String
    init(text intext: String = "PackageConsumer, Version 2.0.0") {
        text = intext + "\n" + Package_BPrime(indent: 1).text
    }
}

Running that, gives us something like this in the console:

PackageConsumer, Version 2.0.0
	Package_BPrime, Version: 1.0.0
		Package_A, Version: 1.0.0

Why “Package_BPrime“?

This was because I found out that there seems to be some built-in module with an exposed module namespace of “Package_B,” and declaring the package with that import name caused a very strange collision. Debugging this took me the better part of a day.