Need to call a function before LinkDrawn

GoJS
1

Hey Walter, is there any event in GOJS which is triggered before LinkDrawn?

The requirement is while I am dragging the linking tool, and just before LinkDrawn is triggered, I need to call a custom function which does some validation and if it returns false, I don’t want the link to be drawn.

2

You can do that in the “LinkDrawn” DiagramEvent listener. For example, to prevent links drawn from “red” nodes to “green” nodes:

  new go.Diagram("myDiagramDiv",
    {
      "LinkDrawn": e => {
        const link = e.subject;
        if (link.fromNode.data.text.indexOf("red") >=0 &&
            link.toNode.data.text.indexOf("green") >= 0) {
          e.diagram.currentTool.doCancel();
          alert("disallowed")
        }
      },
      . . .
3

the custom function i am calling is expecting the current GOJSModel as a parameter and in that model the link is already created in the linkdataarray which causes an issue.

4

Maybe you can use general link validation, described in the validation intro page here.