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usefulness of passing const references to RPCs

Hi everybody,

Maybe it's a stupid idea, but I was wondering if there was a real interest to declare a parameter for an RPC as const reference, as I guess internally the data is copied anyway to be passed on the network. I guess this is still useful to avoid one extra copy of the data, but i was wondering if you guys had an idea on the matter.

for example

 UFUNCTION(Server, Reliable)
 void Server_SetPlayerInfo(const FPlayerInfo& PlayerInfo);

vs

 UFUNCTION(Server, Reliable)
 void Server_SetPlayerInfo(FPlayerInfo PlayerInfo);

FPlayerInfo being a USTRUCT composed of a few FStrings

Product Version: UE 4.20
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asked Feb 22 '19 at 09:56 AM in C++ Programming

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developpeur2000
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const itself does not prevent copying anything. All it's saying is: "This function is not allowed to modify the state of this variable", even if it's a copy. It's most useful to make sure, you don't accidentally set anything in it unwanted.

By using reference, you probably save a copy: the data is transmitted to the server through the network, the server constructs the struct, then passes it to your function. If you don't use a reference, then I believe one more copy is created on the server side.

So yes, I think most usually you'll want to have a const reference in RPCs.

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answered Feb 22 '19 at 10:41 AM

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KristofMorva
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