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How to add an Array of Json Objects to a Json Object?

Hi there,

how is it possible to add an array of Json objects to the main Json Object?

I managed to add a value array:

 // Json object
 TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject);
 // Value array
 TArray< TSharedPtr<FJsonValue> > ValueArray;
 // Create two values and add them to the array
 TSharedPtr<FJsonValue> Value1 = MakeShareable(new FJsonValueString("value1"));    
 TSharedPtr<FJsonValue> Value2 = MakeShareable(new FJsonValueString("value2"));    

 // Add the array to the Json object
 JsonObject->SetArrayField("array", ValueArray);

However I would like to have the array as JsonObjects. That basically the array would be declared as:

 TArray< TSharedPtr  <FJsonObject> > ObjArray;

and I add to the main FJsonObject:

 // create JsonObj array
 TArray< TSharedPtr<FJsonObject> > ObjArray;

 // create a Json object and add a string field
 TSharedPtr<FJsonObject> JsonObj = MakeShareable(new FJsonObject);    
 JsonObj ->SetStringField("Abc", "AbcValue");

 // add the object to the array

 // ***THIS does not work***
 JsonObject->SetArrayField("array", ObjArray);

=====EDIT 1 =====

Compile error:

  • error C2664: 'void FJsonObject::SetArrayField(const FString &,const TArray,FDefaultAllocator> &)' : cannot convert argument 2 from 'TArray,FDefaultAllocator>' to 'const TArray,FDefaultAllocator> &'JsonObject->SetArrayField("array", ObjArray);

  • Reason: cannot convert from 'TArray,FDefaultAllocator>' to 'const TArray,FDefaultAllocator>'

  • No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called


Product Version: UE 4.9
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asked Dec 02 '15 at 12:03 PM in C++ Programming

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2 answers: sort voted first

// create Json values array

TArray< TSharedPtr<FJsonValue> > ObjArray;

// create a Json object and add a string field

TSharedPtr< FJsonObject > JsonObj = MakeShareable(new FJsonObject);

JsonObj->SetStringField("Abc", "AbcValue");

// create a Json value object to hold your Json object

TSharedRef< FJsonValueObject > JsonValue = MakeShareable( new FJsonValueObject( JsonObj) );

// add the object to the array


// THIS should work

AnotherJsonObj->SetArrayField("array", ObjArray);

Modifications for your code to build in bold

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answered May 06 '16 at 08:53 AM

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avatar image ionbordura Jun 13 '16 at 09:40 AM

Hi, thanks for the answer! You missed the brackets when declaring JsonObj as shared pointer. Could you edit that, it might help others:

 TSharedPtr < FJsonObject > JsonObj

Actually the editor removes it, try adding it as Code sample then it appears.

avatar image hsarret Jun 13 '16 at 02:58 PM

Fixed some typos, thanks for letting me know

Glad it helped

avatar image Jayae Jul 13 '16 at 06:02 PM

I'm finding a problem implementing this, isnt it circular?

Reading backwards; you have JsonObj which has an ArrayField of ObjArray. ObjArray contains a pointer to JsonObj, which has a StringField of "Abc", "AbcValue".

I might just be really confused by trying to modify your answer into my own code, but when I try to serialise JsonObj the editor crashes once it reaches 2GB in size ;)

avatar image hsarret Jul 13 '16 at 07:20 PM

I edited to avoid confusion. But there is no problem with code as it was. If you explain your problem we might be able to help you out

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I haven't used JSon in UE so far and "doesn't work" is a bit unspecific, but maybe you're running into the same problem as this poster: https://answers.unrealengine.com/questions/290630/how-to-const-cast-tarray-of-tsharedptr.html

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answered Dec 03 '15 at 10:42 AM

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