Can we have a statement in YANG which constraints the user input string to one of the strings which are permitted? I saw that one can use pattern to match a certain regex, but what if we have strings like "apple", "orange", "strawberry" which are permitted, and the product below must be a member of this set of permissible strings?
leaf product{
type string;
}
YANG has a built-in type named enumeration, which serves the exact purpose you describe.
leaf product {
type enumeration {
enum apple;
enum orange;
enum strawberry;
}
}
This is the type you should use if permitted values are members of a set of string constants. The specifics of the type may be found in RFC 7950, Section 9.6.
Technically speaking, you could also use the string built-in type and restrict it with a pattern that takes a regex argument such as apple|orange|strawberry, but you'd be using the wrong tool for the job.
Advantages of using enumeration instead of above:
enumeration value is a string - one of the enumsenum may be documented with description/referenceenum is (either explicitly or implicitly) assigned a value, an integer that may be used internally by implementations to identify the associated stringenum may get an if-feature statement (YANG version 1.1)