Struct not updating values?

[Keytotruth]

Hi there. I'm not sure if this is the right section, but here goes.
I'm trying to modify some of the variables inside a struct array I made. I loop through the array with a foreach loop but it doesn't seem to do anything, even when I hide unnecessary pins.
I thought maybe the Set Members in Struct function was not working, so I made my own functions to set members:

void AMainCharacter::SetRecharge(FCommand NCommand, const float Time)
{
	NCommand.currentRechargeTime = Time;
}

void AMainCharacter::SetTotalRecharge(FCommand NCommand, const float Time)
{
	NCommand.maxRechargeTime = Time;
}

This is the struct I made:

USTRUCT(Blueprintable)
struct FCommand
{
	GENERATED_USTRUCT_BODY()

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		int32 ID;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		FText CommandName;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		TEnumAsByte<ECommandType> Type;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		UTexture2D* CommandIcon;

	//Base damage or recovery dealt by the command.
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		int32 BaseDamage;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		TEnumAsByte<EElement> CommandElement;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		float ElementPercentage;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		float currentRechargeTime;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Commands")
		float maxRechargeTime;

	FCommand()
	{
		BaseDamage = 0;
		maxRechargeTime = 1000;
		currentRechargeTime = 0;
	}
};

However, even after using those functions, the value printed on screen is still 0.2, which doesn't make much sense. Am I doing anything wrong?

[Zeustiak]

Right now you need to Break and Make the Struct. Not sure when the fix is coming, but Epic is aware of the issue.

[zerofiftyone]

Right now you need to Break and Make the Struct. Not sure when the fix is coming, but Epic is aware of the issue.

Wow, that explains a lot. Been having this issue too but I could never understand what the problem was.

[Keytotruth]

That seems to work for some reason. I expect Epic to get this solved as soon as possible.
I think this is a major issue. After all, it's one of the most basic structures you can have...

Anyways, thanks for the help!

[Stratego99]

As of 4.15 this is still an issue, any word on a fix for this?

[Everynone]

It is working, what issue are you having?

[Stratego99]

It is working, what issue are you having?

[MENTION=2637]Everynone[/MENTION], Thank you for the fast response.

So i'm working on creating a tilegrid based game where each tile has data associated with it that I would like to store in a struct with the following properties:



That struct then becomes an array on which I perform loops to do mass operations on. The problem however starts when I try to store the result back into the array, I have tried nearly all fixes I could think off and found around but those "darn" (due to the profanity filter I could unfortunatly not use a more harsher term) values just refuse to be set in the array.



From this post I gathered that the array is not passed by reference and therefore ultimately won't be set, see red line in the above screenshot.


Also this issue is still unresolved according to the issue tracker

Any suggestions?

EDIT: Currently trying the method proposed here by Techlord

[Everynone]

The key when setting struct array elements is to use SetMembersInStruct, see here, especially the bottom bit:

https://forums.unrealengine.com/show...l=1#post605476

[Stratego99]

I did try that method and got the same result at a few posts down in that thread you linked:

https://forums.unrealengine.com/show...l=1#post605673

With the exact setup the element in the struct array never gets edited, which is the same in my case.

[Everynone]

Works as intended in my humble opinion, see if you can replicate this:



One things that is still not so great is passing struct arrays as a reference.

[Stratego99]

...It worked, but i'm just flabbergasted since I just finished recreating my system to a workaround and now it turns out that it was for nothing.

Thank you very much though!

Lessons learned: Don't do blueprints for more than 10+ hours a day, mistakes like these start creeping in and then you waste time backtracking.

One things that is still not so great is passing struct arrays as a reference.

I believe that I ran into this and must have misinterpreted what the error exactly was, could you expand on this in what cases the above method might fail?

[Everynone]

I believe that I ran into this and must have misinterpreted what the error exactly was, could you expand on this in what cases the above method might fail?

So, consider this:



So then you're thinking, clearly looping through a struct array must be creating copies (pass by value)! Just look at them cheeky navy-blue icons:



All right then, lets do it without the loop:



Duh, I must set it by reference, too!

---

You can tick pass-by-ref checkbox all day long - it's a trap. You can't pass struct by reference, you can't get a pointer to a struct. As far as I know a struct is not a UOBJECT and this behaviour is not supported, not in Blueprints, that is. If I remember correctly I got it working fine in C++.

---

Workarounds exist and they're pretty straightforward, this works like a charm, for example:



That's not even a workaround, tbh, that's how things are.

Hope it helps.

[KrautPotato]

uhm, it's because your c++ code is wrong.

void AMainCharacter::SetRecharge(FCommand* NCommand, const float Time)
{
	NCommand.currentRechargeTime = Time;
}

void AMainCharacter::SetTotalRecharge(FCommand* NCommand, const float Time)
{
	NCommand.maxRechargeTime = Time;
}

Should work.
Cheers.

e/ Oh, 2015, nevermind.

[vb4]

I have given up on understanding this ****.
A while ago I ran head first into the problem and found no way to avoid it.
Right now I'm doing something similar and it works like a charm. I'm not even using "set member in struct", I'm just setting array elements normally in a for-each loop.

I just hope it will continue to work.

Edit:
Actually, now that I think about it, I initially used a function parameter to access the array.
Right now I'm calling the array directly, as I'm in the messy prototyping phase. That probably circumvents the bug, even if it kinda breaks the idea of good programming.

[Stratego99]

[MENTION=2637]Everynone[/MENTION], THANK YOU SO MUCH!!!

I finally get it now due to your clear tutorial and have been able to re-write my grid generation with your advice and it works perfectly now.

I have ended up keeping all changes made to GeneratedMapData within the parent blueprint (might move it to gamestate) and whenever I need a value I just cast to that parent blueprint and get my GeneratedMapData values from that function result.