Question on restricting max inbound links

GoJS
1

So, I have a rectangular node that I want to allow only one (1) inbound link into. However, I want a port on each side of the node for routing convenience. I can set toMaxLinks on each port, but that would still allow a total of four (4) inbound links, one per port. I tried setting toMaxLinks on the node itself, but that didn’t work, as it appears that if a node has ports, they reign supreme.

One idea I had would be to somehow disable (or worst case, remove) the other ports if an inbound link is made.

Any thoughts on how to tackle this?

2

The general answer is to implement a validation predicate: GoJS Validation -- Northwoods Software

Your other suggest solution is also easy to implement in combination with setting GraphObject.toMaxLinks. Define event handlers on the Node, Node | GoJS API and Node | GoJS API, that toggle the visible property or set the toMaxLinks property of all the other ports.

3

Thanks for the reply - I’ll give that a look!

4

For future use by others, here is what I ended up doing. This ensures that only one (1) link can be made between nodes. You could further customize this based on the type of node, but in my case, I need it globally.

// This predicate is true if there are no existing links into the node, false otherwise
function enforceOneLink(fromNode, fromPort, toNode, toPort) {
  return toNode.findLinksInto().count ? false : true;
}

// This predicate is true if there is only one (this one) into the node, false otherwise
function enforceOneReLink(fromNode, fromPort, toNode, toPort) {
  return toNode.findLinksInto().count > 1 ? false : true;
}

// Only allow new links if there are no existing links!
myDiagram.toolManager.linkingTool.linkValidation = enforceOneLink;

// Same as above, for for relinking instead of linking
myDiagram.toolManager.relinkingTool.linkValidation = enforceOneReLink;