Given a computed property
vm.checkedValueCount = ko.computed(function(){
var observables = getCurrentValues(); //an array of ko.observable[]
return _.filter(observables, function(v) { return v() }).length;
});
suppose getCurrentValues() can return different sets of observables which are modified elsewhere in the code (and comes from a more complex structure than an observableArray).
I need checkedValueCount
to update whenever
The problem is that ko.computed
seems to memoize the last returned value and only update when a dependency updates. This handles the first case but not the latter.
What I'm looking for is a way to force checkedValueCount to re-run. Something which I can use like:
changeCurrentValues();
vm.checkeValueCount.recalculate();
Put most simply, given that I have
a = ko.computed(function() { return Math.random() })
how can I force invoking a()
twice to return different values.
I realized my first answer missed your point, and won't solve your issue.
The problem is that a computed will only reevaluate if there is some observable that forces it to re-evaluate. There is no native way to force a computed to re-evaluate.
However, you can get around this with some hackery by creating a dummy observable value and then telling its subscribers that it has changed.
(function() {
var vm = function() {
var $this = this;
$this.dummy = ko.observable();
$this.curDate = ko.computed(function() {
$this.dummy();
return new Date();
});
$this.recalcCurDate = function() {
$this.dummy.notifySubscribers();
};
};
ko.applyBindings(new vm());
}());
Here is a Fiddle showing this approach