Objects References And Deep Copying

Whenever you access any TJSONValue descendants, you are actually dealing with references to them. It means that the following operation will not end up with a new instance of JSON object:

var
    Obj1, Obj2: TJSONObject;
begin
    …
    Obj2 := Obj1[‘subobject’] as TJSONObject;
    Obj1.Free;
end;

In the example, Obj2 is referencing to a subobject of Obj1. That is why we should not release memory of Obj2 since it is also a part of Obj1.

However, we might need to obtain a deep copy of a TJSONObject or TJSONArray. In this case, method Clone can be used:

var
    Obj1, Obj2: TJSONObject;
begin
    …
    Obj2 := Obj1[‘subobject’].Clone as TJSONObject;
    Obj1.Free;
    Obj2.Free;
end;

Here we have to release memory of both objects, because Obj2 is not included in Obj1 anymore. Obj2 is a deep copy of a subobject of Obj1 with exactly the same data, but its own allocated memory.