Array Iterator

[Zumiha]

Hello!
I couldn't find in documentation how to use array address position as value.
For example we have:

\JSONParse{\myJSON}
{
    {
        "array" : [
            {
                "key_a": "one", 
                "key_b" : "two"
            },
            {
                "key_a": "three", 
                "key_b" : "four"
            }
        ]
    }
}

I want to use "pointer to array item" as value.
"Dumb" approach is to add key which will be used as array item number:

\JSONParse{\myJSONid}
{
    {
        "array" : [
            {
                "id": 1, 
                "key_a": "one", 
                "key_b" : "two"
            },
            {
                "id": 2, 
                "key_a": "three", 
                "key_b" : "four"
            }
        ]
    }
}

We can use it as

\begin{itemize}
    \JSONParseArrayMapInline{\myJSONid}{array}{
        \item Group \JSONParseValue{\myJSONid}{array[#1].id}:
            \begin{itemize}
                \item key a: \JSONParseValue{\myJSONid}{array[#1].key_a};
                \item key b: \JSONParseValue{\myJSONid}{array[#1].key_b};
            \end{itemize}
    }
\end{itemize}

This approach demands to use additional key in JSON, but we actually do not need this key, we already have pointer to array item.
So my question comes down to is there command to return iterator for array?
And we could use it as:

...
        \item Group __iterator{array[#1]}__:
...

[jasperhabicht]

If you use \JSONParseArrayMapInline like in your example, the index can simply be accessed with #1. Of course, this would return 0 for the first item, because indices start with zero per default, but you could change this using zero-based=false:

\documentclass{article}
\usepackage{jsonparse}

\JSONParse[zero-based=false]{\myJSON}{
    {
        "array" : [
            {
                "key_a": "one", 
                "key_b" : "two"
            },
            {
                "key_a": "three", 
                "key_b" : "four"
            }
        ]
    }
}

\begin{document}
\begin{itemize}
    \JSONParseArrayMapInline[zero-based=false]{\myJSON}{array}{
        \item Group #1:
            \begin{itemize}
                \item key a: \JSONParseValue{\myJSON}{array[#1].key_a};
                \item key b: \JSONParseValue{\myJSON}{array[#1].key_b};
            \end{itemize}
    }
\end{itemize}
\end{document}

[Zumiha]

Thanks, this works!
Only drawback of this method — if you parsed with [zero-based=false] option, all \JSONParseArrayMapInline later should be used also with this option, otherwise this will break array iteration.

\JSONParseFromFile[zero-based=false]{\myJSON}{JSONs/test.json}

\begin{itemize}
    \JSONParseArrayMapInline[zero-based=false]{\myJSON}{array}{
        \item Group #1:
        \begin{itemize}
            \item key a: \JSONParseValue{\myJSON}{array[#1].key_a};
            \item key b: \JSONParseValue{\myJSON}{array[#1].key_b};
        \end{itemize}
        }
\end{itemize}
====
\begin{itemize}
    \JSONParseArrayMapInline{\myJSON}{array}{
        \item Group #1:
        \begin{itemize}
            \item key a: \JSONParseValue{\myJSON}{array[#1].key_a};
            \item key b: \JSONParseValue{\myJSON}{array[#1].key_b};
        \end{itemize}
        }
\end{itemize}

Result will be:

* Group 1:
    - key a: one;
    - key b: two;
* Group 2:
    - key a: three;
    - key b: four;
====
* Group 0:
    - key a: ;
    - key b: ;
* Group 1:
    - key a: one;
    - key b: two;

I found other inelegant solutions:

1. use \the\numexpr#1+1 as arithmetic inline
2. use \JSONParseSet{zero-based=false} globally before parsing files and work in non-zero-based environment.

[jasperhabicht]

Yes, you are right that you need to state zero-based=false both for parsing and for using the array mapping function. But the two solutions you provide are actually totally fine.

You can also use \JSONParseSet{zero-based=false} in a group which then restricts this setting to the relevant scope if this is required.