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I defined a grouping which has a leaf with mandatory property set to false. But in some cases, I would like to use this grouping and specify that the leaf should be mandatory. How do I achieve this in YANG?

predi
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1 Answers1

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You would use the refine statement when specifying a use of your grouping.

module mandatory-and-grouping {
  namespace "org:example:mandatory-and-grouping";
  prefix "mag";

  grouping my-grouping {
    leaf my-leaf {
      type string;
    }
  }

  container top {
    uses my-grouping {
      refine my-leaf {
        mandatory true;
      }
    }
  }
}

7.13.2. The "refine" Statement

Some of the properties of each node in the grouping can be refined with the "refine" statement. The argument is a string that identifies a node in the grouping. This node is called the refine's target node. If a node in the grouping is not present as a target node of a "refine" statement, it is not refined and thus is used exactly as it was defined in the grouping.

The argument string is a descendant schema node identifier (see Section 6.5).

The following refinements can be done:

  • A leaf or choice node may get a default value, or a new default value if it already had one.
  • A leaf-list node may get a set of default values, or a new set of default values if it already had defaults; i.e., the set of refined default values replaces the defaults already given.
  • Any node may get a specialized "description" string.
  • Any node may get a specialized "reference" string.
  • Any node may get a different "config" statement.
  • A leaf, anydata, anyxml, or choice node may get a different "mandatory" statement.
  • A container node may get a "presence" statement.
  • A leaf, leaf-list, list, container, anydata, or anyxml node may get additional "must" expressions.
  • A leaf-list or list node may get a different "min-elements" or "max-elements" statement.
  • A leaf, leaf-list, list, container, choice, case, anydata, or anyxml node may get additional "if-feature" expressions.
  • Any node can get refined extensions, if the extension allows refinement. See Section 7.19 for details.

RFC7950, Section 7.13.2

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  • Is it possible to achieve similar thing when we need to reuse the same grouping at different place by changing the range value? – Darshan L Mar 21 '19 at 14:07
  • @DarshanL, changing a `range` would be an attempt to change an already defined type of a node in the grouping. This cannot be done, unless you resort to deviations (target would be a schema node, not grouping content). If you need to further restrict a range of values of a node in the grouping, and alternative would be to refine the target with a `must` instead - express the constraint as an XPath expression. You cannot extend the defined range that way, however. – predi Mar 21 '19 at 14:23