On Fri, 13 Feb 2026, Andreas Hof via ntg-context wrote:
> Hi all here,
>
> I have a question in the area of the json module and in general about the
> interaction between Lua and ConTeXt.
>
> In m-json.mkxl we have for example:
>
> interfaces.implement {
> name = "tablefield",
> actions = function(namespace,name)
> local data = field(namespace,name)
> if data then
> context(data)
> end
> end,
> arguments = "2 arguments",
> public = true,
> protected = true,
> }
>
> Means, that, if I ask for a table field from json file the value will be
> typeset through context(data).
>
> Is there any possibility to check the value passed from Lua to ConTeXt on
> ConTeXt level?
>
> I like to use the json module for getting addresses for a mass lettering.
> Prominent examples, where a check of the value from a json-database is needed
> is the title of a person (typeset it plus a space or do nothing if empty),
> or if you need to have alternatives for an opening sentence depending on the
> salutation or gender. Or whatever you can think of in a mass letter depending
> on the dataset ...
For such tasks, one option is convert the data to a lua table, and then typeset
using CLD. For example,
addresses = utilities.json.load("addr.json")
inspect(addresses)
gives
table={
["records"]={
{
["firstname"]="Hildegard",
["location"]="Bingen am Rhein",
["name"]="von Bingen",
["salutation"]="Mrs.",
["street"]="past road 1",
["title"]="",
["zip"]="00000",
},
{
["firstname"]="Hippokrates",
["location"]="Kos",
["name"]="von Kos",
["salutation"]="Mr.",
["street"]="long ago road 1",
["title"]="Dr.",
["zip"]="00001",
},
},
}
So, you can loop over the entries, check for title/salutation and write the
logic in lua (no need to worry about expansion and stuff).
Aditya
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