How to access the alternative of a Field Type

I have a custom field type to parse an ingredient line of a recipe. For example: “2 cups chocolate” or “1 banana” or “1 can Marzano tomatoes, chopped”. As you can see, the format is quite variable so I cannot simply split the string by some delimiter. Instead I have a list of pre-defined measurement units (‘cups’, ‘can’) that I check to split the components.

But now comes the tricky part, my site is multi-lingual and I have a different list of measurements for each alternative. However, when lektor initializes my custom field (value_from_raw) I have no way to get the alternative of the calling record.

Is there a way to get the alternative of a Field Type?

[dairiki]

Ah. If you want access to the record (so that you can access record.alt), you’ll need to resort to returning a “descriptor” from your value_from_raw (and defer further processing of the value until that descriptor’s __get__ is called.)

See Lektor’s MarkdownType for an example of how that’s done.

The issue (IIRC) is that value_from_raw gets called early in the process of reading the .lr file data, before the Record is actually constructed. So at the time value_from_raw is called, there is no record…

[dairiki]

I don’t think it’s used anywhere.

The API is evidently copied from Python’s attribute descriptor API. Maybe, originally, the idea was to use the property decorator to define field descriptors? I don’t know.