Writing a custom Required True rule.

[AJMcKane]

Hi there,

I'm brand new to KO and KO validation and I was wondering if anyone could help point me in the right direction?

I've created a form running as a SPA but I need validation on text areas to activate depending on the previous's select element's value (which is bound to a knockout value).

For example,
self.standardConstruction = ko.observable().extend({ required: true });
self.constructionType = ko.observable().extend({ required: {onlyIf: standardConstruction() === 'Yes'} });

However, I've found the onlyIf statement doesn't allow for anonymous functions and I can't set the array that populates my "[blank] ,'Yes', 'No'" fields to actually equate to true/false in the code behind.

I'm hoping there's a way of writing a custom validation rule that allows me to pass a value, an expected value and then activate the required: true flag based off that!

////Knockout validation rules
//ko.validation.rules['isReqYes'] = {
// validator: function( param, expected) {
// if(param === expected)
// {
// required: true
// }
// },
//
// message: 'This field is required.',
//};

Unfortunately I can't find much documentation and my experience is lacking so I'm making no headway! Any and all help is appreciated :D

Also, thanks for the library, it's been a great help with my project so far!
Regards,
Antony

[crissdev]

Duplicate of #374