javascript - Knockout Validation of two interdependent fields - Stack Overflow

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Consider the following piece of code -

var MyObjectModel = function(myObject){
var self = this;
self.myNumber1 = ko.observable(myObject.number1).trimmed();
self.myNumber2 = ko.observable(myObject.number2).trimmed();

I would like to extend myNumber1 and myNumber2, to add knockout validations such that it throws an error if both are empty, and stays fine if either has a value.

Any idea how I could go about achieving this ?

Consider the following piece of code -

var MyObjectModel = function(myObject){
var self = this;
self.myNumber1 = ko.observable(myObject.number1).trimmed();
self.myNumber2 = ko.observable(myObject.number2).trimmed();

I would like to extend myNumber1 and myNumber2, to add knockout validations such that it throws an error if both are empty, and stays fine if either has a value.

Any idea how I could go about achieving this ?

• javascript
• knockout.js
• knockout-validation

Share Improve this question Follow asked Jan 15, 2013 at 6:01 Vishnu NarangVishnu Narang 60588 silver badges1515 bronze badges

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2 Answers 2

Sorted by: Reset to default 9

You can use an ko.puted to create a function which checks if at least any of both fields is set and onlyIf in the validation to execute the validation conditionally.

var MyObjectModel = function (myObject) {
    var self = this;
    self.myNumber1 = ko.observable(myObject.number1);
    self.myNumber2 = ko.observable(myObject.number2);

    self.numbersHaveNoValue = ko.puted(function () {
        var value1 = self.myNumber1(), value2 = self.myNumber2();
        return !ko.validation.rules.required.validator(value1, true) &&
               !ko.validation.rules.required.validator(value2, true);
    });

    self.myNumber1.extend({ required: { onlyIf: self.numbersHaveNoValue }});
    self.myNumber2.extend({ required: { onlyIf: self.numbersHaveNoValue }});
}

I have created a fiddle: http://jsfiddle/delixfe/aBytt/

var MyObjectModel = function(myObject) {
    var self = this;
    self.myNumber1 = ko.observable(myObject.number1).trimmed();
    self.myNumber2 = ko.observable(myObject.number2).trimmed();

    self.numberCount = ko.puted(function() {
        var count = 0;
        count += self.myNumber1() != '' ? 1 : 0;
        count += self.myNumber2() != '' ? 1 : 0;
        return count;
    }).extend({min:1});
}

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