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75 lines
2.0 KiB
75 lines
2.0 KiB
var _ = require('underscore');
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var ko = require('knockout');
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var dispose = require('./dispose');
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/**
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* An ObservableSet keeps track of a set of values whose membership is controlled by a boolean
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* observable.
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* @property {ko.observable<Number>} count: Count of items that are currently included.
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*/
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function ObservableSet() {
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this._items = {};
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this.count = ko.observable(0);
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}
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dispose.makeDisposable(ObservableSet);
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/**
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* Adds an item to keep track of. The value is added to the set whenever isIncluded observable is
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* true. To stop keeping track of this item, call dispose() on the returned object.
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*
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* @param {ko.observable<Boolean>} isIncluded: observable for whether to include the value.
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* @param {Object} value: Arbitrary value. May be omitted if you only care about the count.
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* @return {Object} Object with dispose() method, which can be called to unsubscribe from
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* isIncluded, and remove the value from the set.
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*/
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ObservableSet.prototype.add = function(isIncluded, value) {
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var uniqueKey = _.uniqueId();
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var sub = this.autoDispose(isIncluded.subscribe(function(include) {
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if (include) {
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this._add(uniqueKey, value);
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} else {
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this._remove(uniqueKey);
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}
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}, this));
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if (isIncluded.peek()) {
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this._add(uniqueKey, value);
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}
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return {
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dispose: function() {
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this._remove(uniqueKey);
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this.disposeDiscard(sub);
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}.bind(this)
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};
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};
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/**
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* Returns an array of all the values that are currently included in the set.
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*/
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ObservableSet.prototype.all = function() {
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return _.values(this._items);
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};
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/**
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* Internal helper to add a value to the set.
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*/
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ObservableSet.prototype._add = function(key, value) {
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if (!this._items.hasOwnProperty(key)) {
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this._items[key] = value;
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this.count(this.count() + 1);
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}
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};
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/**
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* Internal helper to remove a value from the set.
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*/
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ObservableSet.prototype._remove = function(key) {
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if (this._items.hasOwnProperty(key)) {
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delete this._items[key];
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this.count(this.count() - 1);
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}
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};
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module.exports = ObservableSet;
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