FabricJs- Cloning objects loses custom properties

问题

I have set custom properties on SVG objects and on paths within the SVG objects.

Each object I add to the canvas also gets assigned an 'id' property, as well as some others properties that I use to interact with the objects in the app.

So far, when I clone these objects, I have been able to retain the properties that are on the SVG object by storing them in a session variable prior to cloning, then adding them back after cloning.

My problem is with the properties that are set on each of the object.paths. I have an 'id' property for each path, which I use for some functions that can manipulate the paths within the object.

So for example, before I group the object, the object.paths attribute looks like this...

paths: Array(4)
0: klass {id: "_25mm_x_400mm_ROUND", d: "M400.5,60.5A21.52,21.52", fill: "#ccc", dirty: false, stroke: "#000", …}
1: klass {id: "_25mm_x_400mm_ROUND", d: "M400.5,60.5v25c0", stroke: "#000", dirty: false, strokeMiterLimit: 10, …}
2: {id: "shapeTopColor", d: "M400.5,60.5A21.52,21.52", fill: "rgba(0, 0, 0, 0)", dirty: false, stroke: "#000", …}
3: {id: "shapeSideColor", d: "M400.5,60.5v25c0", stroke: "#000", dirty: false, strokeMiterLimit: 10, …}

Then, after ungrouping the object, the object.paths attribute looks like this...

paths: Array(4)
0: klass {type: "path", originX: "left", originY: "top", left: 0.4999999999999982, top: 0.5, …}
1: klass {type: "path", originX: "left", originY: "top", left: 0.5, top: 60.5, …}
2: klass {type: "path", originX: "left", originY: "top", left: 0.4999999999999982, top: 0.5, …}
3: klass {type: "path", originX: "left", originY: "top", left: 0.5, top: 60.5, …}

This breaks some functions that use the 'shapeTopColor and 'shapeSideColor' ids to change fill attributes for each path. So if a user groups an object, then ungroups it, they are no longer able to change the colour of the object.

Here is the code I am using to group objects...

export function groupSelectedItems() {

  canvas = document.getElementById("c").fabric;

  var activegroup = canvas.getActiveGroup();
  var objectsInGroup = activegroup.getObjects();

  var objectIds = [];

  activegroup.clone(function(newgroup) {

      canvas.discardActiveGroup();
      objectsInGroup.forEach(function(object) {
          objectIds.push({
            'id':object.id,
            'componentType':object.componentType,
            'shape': object.shape,
            // paths = object.paths //Tried this but causes errors.
           });
          canvas.remove(object);
      });

      newgroup.setControlsVisibility({'tl': false, 'tr': false, 'bl': false, 'br': false, 'ml': false, 'mr': false, 'mb': false, 'mt': false});
      canvas.add(newgroup);

      //Store the objects id's on to a session variable.
      Session.set('objectIds', objectIds);

      //put original objects id's back onto the new groups objects respectively.
      var objectsInNewGroup = newgroup.getObjects();
      objectsInNewGroup.forEach(function(object, key) {
          Session.get('objectIds').forEach(function(o, i) {
            if (key == i) {
              object.id = o.id
              object.componentType = o.componentType,
              object.shape = o.shape
              // object.paths = o.paths
            }
          });
      });

  });
}

So my question is, how can I clone an object or group and not lose any custom attributes I have set?

回答1:

DEMO

var canvas = new fabric.Canvas('c');
var rect1 = new fabric.Rect({
  id: 1,
  width: 100,
  height: 100,
  fill: 'red',
  componentType: 'a1',
  shape: 'round1'
});
var rect2 = new fabric.Rect({
  id: 2,
  left:10,
  top:20,
  width: 100,
  height: 100,
  fill: 'magenta',
  componentType: 'a2',
  shape: 'round2'
});
var rect3 = new fabric.Rect({
  id: 3,
  left:30,
  top:30,
  width: 100,
  height: 100,
  fill: 'yellow',
  componentType: 'a3',
  shape: 'round3'
});
var group = new fabric.Group([rect1, rect2, rect3]);
canvas.add(group)
canvas.setActiveObject(group);

function cloneObj() {
  group.clone(function(newgroup) {
    canvas.add(newgroup.set({
     left: newgroup.left + 10,
     top: newgroup.top + 10
    }));
    console.log(newgroup);
  }, ['id', 'componentType', 'shape']);
}

canvas {
    border: 1px solid #999;
}

<script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.js"></script>
<button onclick='cloneObj()'>Clone</button>
<canvas id="c" width="700" height="400"></canvas>

clone accepts a callback and array for additional property to include in cloned object.

来源：https://stackoverflow.com/questions/47168736/fabricjs-cloning-objects-loses-custom-properties

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