'BuildPostProcessor' does not implement interface member 'IBuildPostprocessor.LaunchPlayer(BuildLau

🌵 Needle Engine
1

While downgrading or upgrading to new needle version I always get that method LaunchPlayer in NeedleEngineBuildTarget.cs is always a void and according to the IBuildPostprocessor interface needs to be converted to ILaunchPlayer and then I give a return type of null. But why it is not embedded and I need to do it manually always.

Screenshot 2025-05-12 121304
Screenshot 2025-05-12 121304748×177 5.98 KB

2

Hi Samsmeep Singh,

Step-by-Step Plan

  1. Understand the Issue:
    • Unity’s IBuildPostprocessor.LaunchPlayer interface changed its return type from void to ILaunchPlayer? in some Unity versions.
  2. Check Needle Engine Support:
    • Needle Engine often tries to keep up with Unity version changes, but not every update is released simultaneously.
  3. Why Not Embedded?
    • If you upgrade or downgrade Unity, the Needle Engine Unity package may not yet have code that matches your specific Unity version’s interface signature.
    • This mismatch requires manual changes in your local NeedleEngineBuildTarget.cs to adapt to the current signature.
  4. General Solution:
    • Update method signature in your local code to match the Unity API version.
    • Usually:
      public ILaunchPlayer? LaunchPlayer(BuildLaunchPlayerArgs args) => null;
    • Future releases of Needle Engine should include fixes, but there is a lag while maintaining compatibility with multiple Unity versions.

Why is it not handled automatically?

  • Unity API changes fast and third-party tools/packages need to support multiple API signatures.
  • Needle Engine cannot predict every user’s Unity version, so the shipped package favors broad compatibility.
  • Until a Needle Engine update targets your exact Unity version, manual fixes may be needed.
  • See Needle Engine docs on Unity versions and compatibility.

Tip:

  • Always check for latest Needle Engine updates after Unity upgrades.
  • If you encounter similar breaking changes, report them on Needle’s GitHub issues for faster fixes.

Next Steps:

  • Are you targeting a specific Unity version?
  • Is this blocking your workflow?
  • If you like, paste your Unity “Copy Project Info into Clipboard” here so I can better advise which versions should work together.

How to ask good questions:

  • Specify Unity and Needle Engine versions.
  • Attach error logs or screenshots.
  • Describe steps you tried and their results.

Would you like guidance on automating this patch for future upgrades?

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3

Hi, could you please let us know which unity version you’re using?

4

Unity 6.1

5

Thanks, which version are you using exactly? It’s not unlikely that this has been changed in a minor release so the exact version could safe some time when debugging this

6

So for Unity: 6000.1.0f1 and for Needle Engine: 4.4.3