Is it possible to check for an element in a leaf list and return error-message in yang. Please provide an example.
It is a bit unclear what you want to achieve. If you want to:
-
make sure that the leaf-list has at least one element:
leaf-list data { type string; min-elements 1; }
-
make sure that a certain element exists:
leaf-list data { type string; } must "data = 'myvalue'" { error-message "element 'myvalue' must be present"; }
This can be used event for 1. using simple
must "data"
, the advantage is that it allows you to customize the error message; it might have a bit worse performance though; -
have a complex constraint on every element in the list - this is possible too, depending on the constraint you may be able to achieve that with a must statement like this:
leaf-list data { type string; must "my-xpath-expr"; }
or you may need to resort to semantic validation. There are examples of this in
intro/validation
examples (and others), one full chapter of the ConfD user guide is dedicated to this topic too.