Is there anyway I can tell the knockout mapping plugin to subscribe to all property changes call a certain function?
I realize I can manually subscribe to the property change event in this manner:
var viewModel = {
name: ko.observable('foo'),
}
// subscribe manually here
viewModel.name.subscribe(function(newValue){
// do work
})
I would like to be able to generically subscribe though, since my view models may vary, I don't want to hardcode the property names. I created a function that does this, but it may not be the best approach. It works over all browsers except IE7 and below.
Here I take a viewmodel as an argument and try to reflect on it subscribing to the properties:
function subscribeToKO(data) {
$.each(data, function (property, value) {
if (getType(value) == "Object")
data[property] = subscribeToKO(value);
else if (getType(value) == "Array") {
$.each(value, function (index, item) {
item = subscribeToKO(item);
});
}
else {
if (value.subscribe) {
value.subscribe(function (newValue) {
// do work
});
}
}
});
return data;
}
Like I said this works, but since I am using the mapping pluging I was hoping there was a hook I could use to provide it with a function that will generically subscribe to property changes.
Something like:
mapping = {
create: function(options){
options.data.subscribe(function(newValue){
// do work ???
});
}
}
ko.mapping.fromJS(viewModel, mapping);
Any ideas?
Here's a generic approach based on Ryan Niemeyer's dirty flag.
Click here for the JsFiddle.
Html:
<ol>
<li>
Telephone : <input data-bind="value: telephone"/>
</li>
<li>
Address : <input data-bind="value: address"/>
</li>
</ol>
Javascript:
var model = {
telephone: ko.observable('0294658963'),
address: ko.observable('167 New Crest Rd')
};
// knockout extension for creating a changed flag (similar to Ryan's dirty flag except it resets itself after every change)
ko.changedFlag = function(root) {
var result = function() {};
var initialState = ko.observable(ko.toJSON(root));
result.isChanged = ko.dependentObservable(function() {
var changed = initialState() !== ko.toJSON(root);
if (changed) result.reset();
return changed;
});
result.reset = function() {
initialState(ko.toJSON(root));
};
return result;
};
// add changed flag property to the model
model.changedFlag = new ko.changedFlag(model);
// subscribe to changes
model.changedFlag.isChanged.subscribe(function(isChanged) {
if (isChanged) alert("model changed");
});
ko.applyBindings(model);