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subscribable.js
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141 lines (118 loc) · 5.14 KB
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ko.subscription = function (target, callback, disposeCallback) {
this.target = target;
this.callback = callback;
this.disposeCallback = disposeCallback;
this.isDisposed = false;
ko.exportProperty(this, 'dispose', this.dispose);
};
ko.subscription.prototype.dispose = function () {
this.isDisposed = true;
this.disposeCallback();
};
ko.subscribable = function () {
ko.utils.setPrototypeOfOrExtend(this, ko.subscribable['fn']);
this._subscriptions = {};
}
var defaultEvent = "change";
var ko_subscribable_fn = {
subscribe: function (callback, callbackTarget, event) {
var self = this;
event = event || defaultEvent;
var boundCallback = callbackTarget ? callback.bind(callbackTarget) : callback;
var subscription = new ko.subscription(self, boundCallback, function () {
ko.utils.arrayRemoveItem(self._subscriptions[event], subscription);
});
// This will force a computed with deferEvaluation to evaluate before any subscriptions
// are registered.
if (self.peek) {
self.peek();
}
if (!self._subscriptions[event])
self._subscriptions[event] = [];
self._subscriptions[event].push(subscription);
return subscription;
},
"notifySubscribers": function (valueToNotify, event) {
event = event || defaultEvent;
if (this.hasSubscriptionsForEvent(event)) {
try {
ko.dependencyDetection.begin(); // Begin suppressing dependency detection (by setting the top frame to undefined)
for (var a = this._subscriptions[event].slice(0), i = 0, subscription; subscription = a[i]; ++i) {
// In case a subscription was disposed during the arrayForEach cycle, check
// for isDisposed on each subscription before invoking its callback
if (!subscription.isDisposed)
subscription.callback(valueToNotify);
}
} finally {
ko.dependencyDetection.end(); // End suppressing dependency detection
}
}
},
limit: function(limitFunction) {
var self = this, selfIsObservable = ko.isObservable(self),
isPending, previousValue, pendingValue, beforeChange = 'beforeChange';
if (!self._origNotifySubscribers) {
self._origNotifySubscribers = self["notifySubscribers"];
self["notifySubscribers"] = function(value, event) {
if (!event || event === defaultEvent) {
self._rateLimitedChange(value);
} else if (event === beforeChange) {
self._rateLimitedBeforeChange(value);
} else {
self._origNotifySubscribers(value, event);
}
};
}
var finish = limitFunction(function() {
// If an observable provided a reference to itself, access it to get the latest value.
// This allows computed observables to delay calculating their value until needed.
if (selfIsObservable && pendingValue === self) {
pendingValue = self();
}
isPending = false;
if (self.isDifferent(previousValue, pendingValue)) {
self._origNotifySubscribers(previousValue = pendingValue);
}
});
self._rateLimitedChange = function(value) {
isPending = true;
pendingValue = value;
finish();
};
self._rateLimitedBeforeChange = function(value) {
if (!isPending) {
previousValue = value;
self._origNotifySubscribers(value, beforeChange);
}
};
},
hasSubscriptionsForEvent: function(event) {
return this._subscriptions[event] && this._subscriptions[event].length;
},
getSubscriptionsCount: function () {
var total = 0;
ko.utils.objectForEach(this._subscriptions, function(eventName, subscriptions) {
total += subscriptions.length;
});
return total;
},
isDifferent: function(oldValue, newValue) {
return !this['equalityComparer'] || !this['equalityComparer'](oldValue, newValue);
},
extend: applyExtenders
};
ko.exportProperty(ko_subscribable_fn, 'subscribe', ko_subscribable_fn.subscribe);
ko.exportProperty(ko_subscribable_fn, 'extend', ko_subscribable_fn.extend);
ko.exportProperty(ko_subscribable_fn, 'getSubscriptionsCount', ko_subscribable_fn.getSubscriptionsCount);
// For browsers that support proto assignment, we overwrite the prototype of each
// observable instance. Since observables are functions, we need Function.prototype
// to still be in the prototype chain.
if (ko.utils.canSetPrototype) {
ko.utils.setPrototypeOf(ko_subscribable_fn, Function.prototype);
}
ko.subscribable['fn'] = ko_subscribable_fn;
ko.isSubscribable = function (instance) {
return instance != null && typeof instance.subscribe == "function" && typeof instance["notifySubscribers"] == "function";
};
ko.exportSymbol('subscribable', ko.subscribable);
ko.exportSymbol('isSubscribable', ko.isSubscribable);