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 ?
You can use an ko.computed 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.computed(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.net/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.computed(function() { var count = 0; count += self.myNumber1() != '' ? 1 : 0; count += self.myNumber2() != '' ? 1 : 0; return count; }).extend({min:1}); }