JSON array at top level of response

[unktomi]

Hello,
I was trying to use VaRest to talk to a Philips Hue bridge. That device sends json responses with an Array not Object at the top level. It seems the response in VaRest is hardcoded to VaResttJsonObject. Apparently having an Array is legal Json:
RFC 4627:
"A JSON text is a serialized object or array."
Not sure what the best way to fix this is.

[ufna]

Hi @unktomi ,

Unfortunately top-level arrays are not supported by Epic's deserializer, but you can try to frame top level array as variable manually:

[ufna]

Added as HowTo to the docs: https://hiazma.atlassian.net/wiki/display/VAR/HowTo%3A+Read+top-level+arrays

[unktomi]

Thanks for the workaround - however the Epic serializer as of at least 4.12 does seem to support deserializing a JSON Array:
template
static bool Deserialize( const TSharedRef< TJsonReader >& Reader, TArray< TSharedPtr >& OutArray )

[ufna]

Thanks, I'll check it tomorrow

[gwythaint]

One has to double quote the "myarray" field name.

[saidmoya12]

@ufna Responsecontent No work with lastest VaRest for UE4.19

[hgsujay]

For those who are looking for the solution here is what I did.
I added a new class in my game module and got this to work.
Added a new class named VaRestBpLibrary.cpp that inherits UBlueprintFunctionLibrary.
Added the Json and VaRest as dependencies
PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "Http", "Json", "VaRest" });
And then added the following function in the Library.
VaRestBpLibrary.h file

#pragma once

#include "CoreMinimal.h"
#include "VaRestJsonObject.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "VaRestBpLibrary.generated.h"

UCLASS()
class MYGAME_API UVaRestBpLibrary : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()
	UFUNCTION(BlueprintCallable, Category = "VaRestBpLibrary", meta = (DisplayName = "Decode Top Level Array"))
	static TArray<UVaRestJsonObject*> DecodeTopLevelArray(FString Response);
};

VaRestBpLibrary.cpp

#include "VaRestBpLibrary.h"

TArray<UVaRestJsonObject*> UVaRestBpLibrary::DecodeTopLevelArray(FString Response)
{	
	TSharedRef<TJsonReader<>> Reader = TJsonReaderFactory<>::Create(*Response);
	TArray<TSharedPtr<FJsonValue>> OutArray;
	TArray<UVaRestJsonObject*> FinalArray;
	if (FJsonSerializer::Deserialize(Reader, OutArray))
	{
		for (TSharedPtr<FJsonValue> JsonValue : OutArray)
		{
			const TSharedPtr<FJsonObject>* JsonObject;
			JsonValue->TryGetObject(JsonObject);
			UVaRestJsonObject* VaRestJsonObject = NewObject<UVaRestJsonObject>();
			VaRestJsonObject->SetRootObject(JsonObject->ToSharedRef());
			FinalArray.Add(VaRestJsonObject);
		}
	}
	return FinalArray;
}

This creates a Blueprint node that can decode the top-level array and it returns an Array of VaRestJsonObjects, which you can use in the blueprints.
For the input node just plug in the response string(use Get ResponseContent as String node)