Unity debugger - how to debug only one instance of a component

[Piotr_Swierk]

How to make debugger break on a certain line, but only in certain instance of a component.

I mean, for example I’ve got 100 units in scene, each one has own Health.cs component, and I want to debug some line in it, when the health is saved by Saving system. Problem is that Debugger break in every instanace and I need to do a lot of clicking for it break at certain component, that is attached to certain unit, that health for example was damaged.

[bixarrio]

You can’t really do it easily, but there are ways;
one (quite simple) way would be to add a flag to the units that you can set in the inspector. Then, you can add a small check in the code for this flag and put the breakpoint in the check. Unfortunately, you’d have to have the code ready at design time because you can’t edit it at runtime

This is the flag

[SerializeField] bool debugUnit;

Now, in the inspector you can find the unit and check the box in the inspector. In the spot you want the breakpoint, add this

if (debugUnit)
{ // put the breakpoint on this line
}

Now the debugger will only break in the unit where the breakpoint is set and you can step through that. You don’t need code in the if, just the braces so you can put the breakpoint on the brace. The code will only hit the brace if the flag is set, so it will only hit the breakpoint then

Note: the next bit works in Visual Studio. I don’t know if it will work in VSCode
Another way is to figure out (at runtime) what the unit’s unique id is. You could use the hash code of the instance to determine this. Then, you can set a condition on the breakpoint to check the hash code and it will only break if the condition is met.

You could also use the debugUnit flag above with conditions, but conditions slows the code down tremendously.

To set a condition on a breakpoint, right-click on the dot and pick Conditions...

For the flag, the condition would be something like debugUnit == true

One other thing is that you could probably get away with not using the debugger. It depends on what you are trying to check. In most cases you could just write to the console. For this, I’d use the debugUnit and then just write the data if the flag is set

if (debugUnit)
{
    Debug.Log(DataImInterestedIn);
}

In my day job I debug a lot, but with Unity I seldom do. I’ve found Unity to start slowing down the longer I debug so I’ve learned to get what I need without running the debugger.

[Brian_Trotter]

I’m also a Debug without the Debugger sort of person.
This solution looks like a good way to select a specific instance. Put the breakpoint on the Debug.Log in the if(debugUnit) body and it should only break on the instances that debugUnit are checked.