A Swift package for working with GraphViz.

• Swift 5.1+
• GraphViz (only for rendering)

import GraphViz

var graph = Graph(directed: true)

let a = Node("a"), b = Node("b"), c = Node("c")

graph.append(Edge(from: a, to: b))
graph.append(Edge(from: a, to: c))

var b_c = Edge(from: b, to: c)
b_c.constraint = false
graph.append(b_c)

// Produce DOT language representation
let dot = DOTEncoder().encode(graph)

// Render image using dot layout algorithm
let data = try! graph.render(using: .dot, to: .svg)
let svg = String(data: data, encoding: .utf8)!

digraph {
  a -> b
  a -> c
  b -> c [constraint=false]
}

Note: The render(using:to:) method requires that the GraphViz binary corresponding to the specified layout algorithm is accessible from the current $PATH.

To use the following interface, add "GraphVizBuilder" to your package's dependencies and replace import GraphViz with import GraphVizBuilder as needed.

import GraphVizBuilder

let graph = Graph(directed: true) {
    "a" --> "b"
    "a" --> "c"
    ("b" --> "c").constraint(false)
}

Note: Swift 5.1 may require explicit typecast expressions in order to reconcile use of custom edge operators like -->. (error: ambiguous reference to member '-->')

Add the GraphViz package to your target dependencies in Package.swift:

import PackageDescription

let package = Package(
  name: "YourProject",
  dependencies: [
    .package(
        url: "https://github.com/SwiftDocOrg/GraphViz",
        from: "0.1.0"
    ),
  ]
)

Add GraphViz as a dependency to your target(s):

targets: [
.target(
    name: "YourTarget",
    dependencies: ["GraphViz"]),

To render graphs to SVG, PNG, and other formats, you must have GraphViz executables (e.g. dot) installed on your system and accessible from $PATH. You can install GraphViz from the command line:

# macOS
$ brew install graphviz

# Linux (Ubuntu)
$ sudo apt-get install graphviz

MIT

Mattt (@mattt)