why fabricjs kclass fromobject returning undefined on new version? - undefined

Question

yesterday i have changed fabricjs version in our application. suddenly kclass.fromObject returning undefined.
my previous version is 1.7.22 and currently using 3.6.1 https://cdnjs.cloudflare.com/ajax/libs/fabric.js/3.6.1/fabric.min.js
kclass.fromobject returning undefined. but objects[i] has data.
> var klass = fabric.util.getKlass(objects[i].type);
> console.log(klass.fromObject(objects[i])); //returning undefined on 3.6.1
> fabricObj.add(klass.fromObject(objects[i]));
could you please let me know how to fix this issue?
Here is the screenshot

Answer 1

Your objects array contains just plain javascript objects that represent serialized Fabric objects (like path, circles, whatever).
Before rendering these plain javascript objects you need to transform them in Fabric objects. This process is called deserialization.
Your code does it, but only the if the async property of the variable klass is true.
It happens here:
var klass = fabric.util.getKlass(objects[i].type);
if (klass.async) {
klass.fromObject(objects[i], function (img) {
canvas1.add(img);
});
}
The object is deserialized, passed as an argument to the callback function and then added to the canvas, and this is great.
The problem is in the else branch of your conditional, where nothing of that happens. The only code present is this:
else {
console.log(objects[i]);
canvas1.add((objects[i]));
}
Here you are trying to add the plain object to the canvas, and that triggers an error.
One simple solution is to remove the if / else and always execute the deserialization step. If for other reasons you need to maintain the if / else conditional, you can simply deserialize the object in the else path too.
Here is a working Fiddle that preserves the conditional.
Why did it work in the previous version of Fabric? It is hard to say. Maybe that type of object was marked as async, so triggering the right path. Or maybe the canvas.add method was automatically deserializing javascript objects.