copy a JSONValue

[Daniel Kozak via Digitalmars-d-learn]

On Friday, 26 August 2016 at 06:56:06 UTC, Alex wrote:
> Hi everybody,
> I'm little at loss: as documented, a JSONValue is only shallow 
> copied:
>
> ...
>
> So the effect that the code of "j" is altered was expected.
>
> The question is: how to make a deep copy of a JSONValue? Is 
> there a simple way without copying the source string around? 
> Or, would this be the simplest way?
>
> Thanks in advance
> Alex

Another way is to implement deepCopy by yourself (something like 
below)

import std.json;
import std.stdio;

JSONValue deepCopy(ref JSONValue val)
{
     JSONValue newVal;
     switch(val.type)
     {
         case JSON_TYPE.STRING:
             newVal = JSONValue(val.str.idup);
             break;
         case JSON_TYPE.OBJECT:
             foreach (string key, value; val)
             {
                 newVal[key] = value.deepCopy;
             }
             break;
         case JSON_TYPE.ARRAY:
             foreach (size_t index, value; val)
             {
                 newVal[index] = value.deepCopy;
             }
             break;
         default:
             newVal = val;

     }
     return newVal;
}

void main()
{
     string s = "{ \"language\": \"D\", \"rating\": 3.14, 
\"code\": 42 }";
     JSONValue j = parseJSON(s);
     writeln("code: ", j["code"].integer);

     auto j2 = j.deepCopy;
     j2["code"] = 43;
     writeln("code of j2: ", j2["code"].integer);
     writeln("code of j: ", j["code"].integer);
}