How to use ko.validation.group function

Question

I am trying to use knockout.validation plugin. I created an exampleViewModel :

function exampleViewModel() {
   this.P1 = ko.observable().extend({ required : true });
   this.P2 = ko.observable().extend({ required : true });
   this.P3 = ko.observable().extend({ required : true });
   this.P4 = ko.observable().extend({ required : true });

   this.errors = ko.validation.group(this);
}    

In the above view model i created a validation group named errors for the current object. Now if any validation rule fails on any 1 property out of 4 than this errors property contains an error message.

My question is , if i want to create a validation group of only 3 properties (P1, P2, P3) out of 4 than how can i do this ?

Solution 1

This worked well for me. Rather than grouping on this, create a proxy object that holds the properties you want validated.

this.errors = ko.validation.group({
    P1: this.P1,
    P2: this.P2,
    P3: this.P3
});

If you do this, consider using validatedObservable instead of group. Not only do you get the errors, but you can collectively check if all the properties are valid using the isValid property.

this.validationModel = ko.validatedObservable({
    P1: this.P1,
    P2: this.P2,
    P3: this.P3
});

// is the validationModel valid?
this.validationModel.isValid();
// what are the error messages?
this.validationModel.errors();

Solution 2

As described in the documentation the right way to validate only specific observables is:

this.errors = ko.validation.group([this.P1, this.P2, this.P3]);