Conditional Validation Pattern Match

[Andrew McShane]

Hi all, I am trying to conditionally validate an address postcode against a specific RegEx but I only want to do this if my postcode is a UK postcode. Something does have to be entered so it is a required field but the pattern should not always apply. So far I have gotten this;

    self.PostCode = ko.observable().extend(

        {

            required: true,

            maxLength: 20,

            pattern: patterns.postcode

        });

This works fine for a UK format postcode but not anything else

I have also tried this;

    self.PostCode = ko.observable().extend(

        {

            required: { onlyIf: function () { self.CountryId === "GB" } },

            maxLength: 20,

            pattern: patterns.postcode

        });

But this does not work.

Anybody got any pointers/ideas?

[Andrew McShane]

No matter, finally figured it out myself with this

    self.PostCode = ko.observable().extend(

    {

        required: true,

        maxLength: 20,

        pattern: ko.pureComputed(function() { 

            return self.CountryId() === 'GB' ? patterns.postcode : ''

        })

    })