Decode JSON with mochijson2 in Erlang

Question

I have a var that has some JSON data:

A = <<\"{\\\"job\\\": {\\\"id\\\": \\\"1\\\"}}\">>. 

Using mochijson2, I decode the data:

Answer 1

My favourite way of handeling mochijson data is replacing all the struct's with hash maps after which they can be cleanly pattern matched. To do so I wrote this easy to understand function:

structs_to_maps({struct, Props}) when is_list(Props) ->
    lists:foldl(
        fun({Key, Val}, Map) ->
            Map#{Key => structs_to_maps(Val)}
        end,
        #{},
        Props
    );
structs_to_maps(Vals) when is_list(Vals) ->
    lists:map(
        fun(Val) ->
            structs_to_maps(Val)
        end,
        Vals
    );
structs_to_maps(Val) ->
    Val.

Here is an example of how to use it:

do() ->
    A = <<"{\"job\": {\"id\": \"1\"}}">>,
    Data = structs_to_maps(mochijson2:decode(A)),
    #{<<"job">> := #{<<"id">> := Id}} = Data,
    Id.

This has many advantages especially when working with incoming data that can have an unexpected shape.