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Cannot delete task using eachTask


#1

Hi,

I wanted to delete all children belonging to a parent. I haven’t seen a public API for that yet so this is what I did initially.

gantt.eachTask((task) => {
	gantt.deleteTask(task);
}, parent);

However, it throws the following error.

I guess this is similar to the ConcurrentModificationException in Java, where you can’t delete when looping the task? If that is the case, then it should probably handle the error gracefully rather than crashing the application?

Is there any better way to achieve what I want?

My current way of doing is

const childrens = gantt.getChildren(parent);
childrens.forEach((taskId) => {
	if (gantt.isTaskExists(taskId)) {
		gantt.deleteTask(gantt.getTask(taskId));
	};
});

I am also wondering if there is any way to do a batchDelete, currently there is a batchUpdate.

void eachTask ( function code , [ string|number parent , object master ] );

May I also know what exactly is the master parameter for? Any example?

Thanks.


#2

Hello Joseph,
By default, when you delete a parent task, all its children are deleted. You can change that by disabling the cascade_delete option:
https://docs.dhtmlx.com/gantt/api__gantt_cascade_delete_config.html

In our samples, you can find the same method as you use for deleting tasks

"del": function (task_id) {
  if(gantt.isTaskExists(task_id)) gantt.deleteTask(task_id);
  return task_id;
},

https://docs.dhtmlx.com/gantt/samples/02_extensions/09_multiselection.html


If that is the case, then it should probably handle the error gracefully rather than crashing the application?

Gantt shouldn’t crash in that case. If your app crashes because of that, maybe it is related to Angular/React or the solution implementation.
Here is the video that demonstrates that Gantt continues working after an attempt of deleting an unexisting task:
https://files.dhtmlx.com/30d/eb514d616e6f27bc5da8e6d6a9256e52/vokoscreen-2019-09-10_15-29-01.avi


I am also wondering if there is any way to do a batchDelete, currently there is a batchUpdate.

If you want to process several tasks simultaneously, you can use the batchUpdate function even for deleting tasks.

You can see the difference in the following snippet:
http://snippet.dhtmlx.com/ed673a337
And here is another snippet with 30000 tasks (be careful, it might take 5-10 minutes to delete tasks!):
http://snippet.dhtmlx.com/4518a2779


void eachTask ( function code , [ string|number parent , object master ] );

May I also know what exactly is the master parameter for? Any example?

It is an object or a variable that can be used inside the eachTask as this:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this

Here is an example:
http://snippet.dhtmlx.com/28d14d9b3


#3

Hi @ramil,

That’s good to know, will keep it in mind.

I saw the sample, and it indeed is not crashing. I’m not why yet, but the stack trace does point to the library itself. I am trying to delete the task when I receive an event from websocket (if I recall correctly now). Nothing fanciful. I can try to add some error handler, and see how it goes from there.

Thanks, I will try it. Also to verify, whatever is done inside eachTask is run sequentially right even though it is wrapped inside batchUpdate. Example:

gantt.batchUpdate(function () {
    gantt.eachTask(function(task){
      gantt.deleteTask(task.id)
      console.log('test')
    })
  })

console.log will always be called after deletedTask sequentially before moving to the next task even in the batchUpdate mode?

I see, thanks!


#4

Hello Joseph,

Thanks, I will try it. Also to verify, whatever is done inside eachTask is run sequentially right even though it is wrapped inside batchUpdate. Example:

gantt.batchUpdate(function () {
    gantt.eachTask(function(task){
      gantt.deleteTask(task.id)
      console.log('test')
    })
  })

console.log will always be called after deletedTask sequentially before moving to the next task even in the batchUpdate mode?

Yes, console.log('test') will be called right after the task is deleted.
Here is the demo:
http://snippet.dhtmlx.com/e6e58970e


#5

Hi @ramil,

Thanks for the clarification.

The API was somehow confusing as it’s called batchUpdate.


#6

Hello Joseph,
Do you have any suggestions on how that method should be named?
I will forward that information to the dev team.