instantiation.md

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default	Instantiation	3	Options Generics Specialized constructors Static #.from method

Instantiation

Instantiating a graphology Graph object is merely an issue of requiring an implementation and calling it with some options.

Note that if you need to create a Graph using some serialized data or another Graph's data, you should probably check the static #.from.

import Graph from 'graphology';

// Here you go:
const graph = new Graph();

// With options:
const graph = new Graph(options);

Options

• allowSelfLoops [boolean] true: should the graph allow self-loops?
• multi [boolean] false: Should the graph allow parallel edges?
• type [string] "mixed": Type of the graph. One of directed, undirected or mixed.

Examples

// Creating a multi-graph with no self-loops
const graph = new Graph({multi: true, allowSelfLoops: false});

Generics

The Graph class TypeScript declaration exposes three optional generics that you can use to restrict, in this order: node attributes, edge attributes and finally graph attributes.

The given types must extend Attributes, which is a shorthand for {[name: string]: any}.

type NodeAttributes = {
  label: string;
  color: string;
}

type EdgeAttributes = {
  weight: number;
}

type GraphAttributes = {
  name?: string;
}

const graph: Graph<NodeAttributes, EdgeAttributes, GraphAttributes> = new Graph();

Specialized constructors

Rather than providing tedious options to the constructor, one can use one of the many handy constructors provided by the implementation to create the desired graph:

import {MultiDirectedGraph} from 'graphology';

const myCustomGraph = new MultiDirectedGraph();

By default, the Graph object is a simple mixed graph, but here are the different naming "components" that you can use to instantiate a more complex graph:

• Graph with parallel edges?: Multi or none (simple graph).
• Type of the graph?: Directed, Undirected or none (mixed graph).

Then to build the name, one must order the components likewise:

Multi? + Type? + Graph

List of all the specialized constructors

DirectedGraph
UndirectedGraph
MultiGraph
MultiDirectedGraph
MultiUndirectedGraph

Static #.from method

Alternatively, one can create a graph from a serialized graph or another Graph instance using the static #.from method:

Example

const graph = Graph.from(data);

// Need some options?
const graph = Graph.from(data, options);

// Also works with typed constructors
const graph = UndirectedGraph.from(data);

Arguments

• data Graph|SerializedGraph: pre-existing data to give to the constructor. This data can either be an existing Graph instance, and in this case both nodes & edges will be imported from the given graph, or a serialized graph whose format is described here.
• options [object]: options passed to the created graph.

Note that graphology will throw an error if you try to instantiate a typed constructor using inconsistent options.