Parsing JSON responses in c++

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Philip Alexander Prates Machado asked Oct 2, '20

Parsing JSON responses in c++

I cant figure out how to handle json data in c++, in my case i am doing a get match and getting the response on the call back which returns a "FGetMatchResult" struct called "result".

In UE4 blueprints you would split the struct and get the members value and then drag from that and use a node called " Get Object Field", looking at this one would assume that something like the following would work:

result.Members[x].Attributes.GetObjectField(params);

Unfortunately this doesnt work and i cant find any documentation anywhere on how you are suposed to call this kind of stuff in c++, please let me know of any documentation that i missed or how this is done.

unreal

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Answer 1 · 2020-10-03T08:44:52Z

James Lennon answered Oct 3, '20

The way I have been doing it is with reading the plugin source code, reading the API reference for the call I want, and heavy usage of the auto complete (Visual Assist works but I use Rider for Unreal) to see what data is returned.

I haven't used FGetMatchResult in a project yet but typing it into a file gives me a few options:

Result.MatchId() is an FString
Result.Members is a TArray<FMatchmakingPlayerWithTeamAssignment>
Some other things as well, the source is here.

The reason you have to do it with a get fields is the C++ data types haven't been setup to be used with blueprint directly (in most cases it cannot be setup easily from what I can see). In C++ you don't have that restriction so you can work with the data types directly. There is an exception with JSON objects, those you still have to get/set field.

Edit:

Saw in the code you were trying to access Attributes which is a TSharedPtr so you would need to dereference it before accessing it. UE4 Docs on that.

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Philip Alexander Prates Machado commented · Oct 03, 2020 at 09:29 AM

I did not manage to dereference the variable, the methos "listChildren()" wasnt recognized by intelisense and did not compile BUT after using the arrow reference i managed to find "toJSONString()", i did try to use arrow reference before but intelisense didnt show anything for some reason.

At this point intelisense has made me lose more time than help.

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James Lennon Philip Alexander Prates Machado commented · Oct 03, 2020 at 08:01 PM

Default intellisense in Visual Studio is terrible with UE4, most people recommend VAX or Resharper if you are using Visual Studio. I use Rider for Unreal which has Resharper built into it (it's in free open beta for now).

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