<![CDATA[Copy objects -> copy gets slower]]>Hi all,
I have following situation:

QtObject {
    id: blub
    property var obj: ({}) 
}

This property is changed regularly.
The new value is received by a signal and then copied.
But it gets slower with each copy.
For example, the first copy takes 180ms, after a few times it takes 600ms.

I tried different ways to copy it:

1) blub.obj = newValue
2) blub.obj = JSON.parse(JSON.stringify(newValue))
3) blub.obj = Object.assign({}, newValue);

What am I doing wrong?
How can I prevent it from slowing down with every copy?

]]>https://forum.qt.io/topic/163397/copy-objects-copy-gets-slowerRSS for NodeTue, 09 Jun 2026 01:58:53 GMTWed, 01 Oct 2025 12:48:00 GMT60<![CDATA[Reply to Copy objects -> copy gets slower on Thu, 02 Oct 2025 08:50:09 GMT]]>Thanks for your answer.
In meanwhile I was able to solve this problem.
I think it was related to the singleton.
The QtObject blub was in a singleton-qml-module.
Now I moved this QtObject to the main-qml-module.
Now the copy is much faster and it does not get slower.

]]>https://forum.qt.io/post/832325https://forum.qt.io/post/832325Thu, 02 Oct 2025 08:50:09 GMT<![CDATA[Reply to Copy objects -> copy gets slower on Thu, 02 Oct 2025 08:16:24 GMT]]>@MHermann
Others will know more than I. Just some thoughts.

  • Just how big is "big"? MBs? GBs?
  • I can imagine/guess that after the initial setting of the property it will destroy its current value before replacing it with a new one. That could add (quite?) some time to copies after the first time?
  • Is this specifically a JSON issue? If you create a property which is, say, a huge string do you see the same slow down over time?
  • Are you able to test with the last Qt 5.15 instead of your 5.12?
]]>https://forum.qt.io/post/832321https://forum.qt.io/post/832321Thu, 02 Oct 2025 08:16:24 GMT<![CDATA[Reply to Copy objects -> copy gets slower on Thu, 02 Oct 2025 05:48:32 GMT]]>Hi,

I am using Qt5.12.7.
I am developing the app on Linux and then it gets cross-compiled to run Raspbian.
newValue is a big json-object.

At the moment I don't have a minimal example.

Has anyone ever had the problem that copying values ​​becomes slower over time?

]]>https://forum.qt.io/post/832317https://forum.qt.io/post/832317Thu, 02 Oct 2025 05:48:32 GMT<![CDATA[Reply to Copy objects -> copy gets slower on Wed, 01 Oct 2025 16:00:21 GMT]]>Hi,

Which version of Qt ?
On which OS ?
What is newValue ?

Can you provide a minimal compilable example that shows this issue ?

]]>https://forum.qt.io/post/832301https://forum.qt.io/post/832301Wed, 01 Oct 2025 16:00:21 GMT