在终端中输入以下命令：

1.在项目根目录下运行命令：

$ swift package update

2.将“Package.swift”文件中的依赖项更改为：

dependencies: [
    .package(url: "https://github.com/anthonygoddard/antlr4-swift.git", from: "4.8.0")
],

3.添加Antlr4 Grammar文件夹（即包含.g4文件的文件夹）到“Sources”目录下。

4.在“Package.swift”文件中添加以下内容：

let antlr4Target = Target(
    name: "MyAntlr4Target",
    dependencies: [
        .target(name: "MyTargetWithGrammarFiles"),
        .product(name: "Antlr4", package: "antlr4-swift")
    ]
)

targets: [
    .target(name: "MyTargetWithGrammarFiles", path: "Sources", sources: ["MyTargetWithGrammarFiles"]),
    antlr4Target
]

5.现在运行以下命令将会成功构建Antlr4项目：

$ swift build