02 Create Nodes Sources - Tutorial: Graph Builder [yFiles for HTML]

Loading data from different sources

In this step, you will learn how to use different data sources for nodes.

GraphBuilder can import data from multiple sources. All node sources that are presented in this step are combined in the graph on the right. Nodes that are retrieved from the same data source have the same color.

Note

Give data items a unique identifier. It will ensure the correct connection of edges as well as updating the graph correctly after changes in the business data. If null is set for an id provider, the item itself will be used as identifier.

In our examples, we add a property named id to the business data.

Import nodes from an iterable

GraphBuilder accepts different types of data collections. The most commonly used collection is probably the Array.

const nodeData = [{ id: '00' }, { id: '01' }, { id: '02' }]

// nodes source for the turquoise nodes
const nodesSource = graphBuilder.createNodesSource(
  nodeData,
  (item) => item.id
)

Another one is the IEnumerable<T>. The id provider function retrieves the identifiers for the nodes.

IEnumerable<T> implements the iterable protocol, and therefore all yFiles for HTML collections are accepted, as well. Since they are live collections, they become useful when updating the graph with changing data.

const nodeData = IEnumerable.from([{ id: '10' }, { id: '11' }, { id: '12' }])

// nodes source for the blue nodes
const nodesSource = graphBuilder.createNodesSource(
  nodeData,
  (item) => item.id
)

If you have organized the data in a Map for easy and fast access by a key, you can pass it to GraphBuilder as is. The map key of an item is passed to the id provider function as a second parameter and can be used as the identifier or a part of it.

const nodeData = new Map<string, { id: string }>()
nodeData.set('node1', { id: '30' })
nodeData.set('node2', { id: '31' })
nodeData.set('node3', { id: '32' })

// nodes source for the red nodes
const nodesSource = graphBuilder.createNodesSource(
  nodeData,
  (item, key) => item.id
)

Passing data in a Object is handled similar to using a Map. Instead of the key, the property name is available in this case.

const nodeData = {
  node1: { id: '20' },
  node2: { id: '21' },
  node3: { id: '22' }
}

// nodes source for the orange nodes
const nodesSource = graphBuilder.createNodesSource(
  nodeData,
  (item, name) => item.id
)

Import nodes from a generator function

Especially with dynamic data, generator functions can be very useful. If a NodesSource is created from a generator function, it is very easy to update the data as it is described in the tutorial step about updating the graph. In the following example the limit might be variable and the NodesSource will provide the data accordingly.

function* nodes(): Generator<{ id: string }> {
  for (let i = 0; i < limit; i++) {
    yield { id: `4${i}` }
  }
}

// nodes source for the brown nodes
const nodesSource = graphBuilder.createNodesSource(nodes, (item) => item.id)

Note	Please have a look in this tutorial step’s demo code in `create-nodes-sources.ts` and play around with the different ways to import business data.