Need a must constraint while add leaf value

YANG
1

Hi,
I have a model like list a { leafref b {type string } } . Whenever a value is added under one of the list entry a in leafref list, need to check this new value should not present across all list entry’s of a’s leafrefs. Is this possible to achieve through must constraint.

Thanks
Phani

2

Hi,

this can be done also without must statement - using YANG’ s “unique” statement in list:

list a {
  key "something";
  unique "b";
  leaf b {
    type leafref { ... } 
  }
}

(see e.g. https://tools.ietf.org/html/rfc7950#section-7.8.3 )

If you really need need to use statement, you can do something like this:

list a {
  key "something";
  leaf b {
    must "count(../../a[b=current()]) == 1";
    type leafref { ... } 
  }
}

(number of all the list “a” entries that have value b equal to “b” being validated, must be equal to 1)

3

Hi Joseph,
Thanks for the reply. It was small mistake in the above question. leaf b is leaf-list b. model goes as follows.

   list a {
     key  "something";
     leaf-list b {
         type string;  --- This string needs to be unique across all list's leaf list.
      }
 }

Thanks
Phani