Obtaining values for custom fields in a dataflow

[mikecarruthers26]

I have created a dataflow triggered on a course completed event.
I can get the data from the user and course, but the custom fields exist in an array:
customfields:
- { type: checkbox, value: '0', name: SpLD, shortname: submission_assignmentnotes }
- { type: text, value: KF123, name: cms_id, shortname: cms_id }
- { type: text, value: '62', name: volunteer_id, shortname: volunteer_id }
- { type: text, value: KF123, name: pun, shortname: pun }

How can I write an expression to obtain the value of the custom field with name = 'cms_id'.
if I use custom fields[2].value this assumes that the second field will always be cms_id but that's not the case.

Is there any documentation on the valid functions that may be used in an expression?

[brendanheywood]

The expressions language is from symphony:

https://symfony.com/doc/current/reference/formats/expression_language.html

There is a bunch of additional functions which have been made available inside expressions here:

https://github.com/catalyst/moodle-tool_dataflows/blob/MOODLE_401_STABLE/classes/local/provider/expression_provider.php#L76-L85

You might be able to filter this as-is using an array operator:

https://symfony.com/doc/current/reference/formats/expression_language.html#array-operators

If neither of those work and you need to pull in a php level function and expose it then that should be an easy pull request