forerunnerdb
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A NoSQL document store database for browsers and Node.js.
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<h1 class="page-title">Source: Condition.js</h1>
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<pre class="prettyprint source linenums"><code>"use strict";
var //Overload = require('./Overload'),
Shared,
Condition;
Shared = require('./Shared');
/**
* The condition class monitors a data source and updates it's internal
* state depending on clauses that it has been given. When all clauses
* are satisfied the then() callback is fired. If conditions were met
* but data changed that made them un-met, the else() callback is fired.
* @class
* @constructor
*/
Condition = function () {
this.init.apply(this, arguments);
};
/**
* Class constructor calls this init method.
* This allows the constructor to be overridden by other modules because
* they can override the init method with their own.
* @param {Collection|View} dataSource The condition's data source.
* @param {String} id The id to assign to the new Condition.
* @param {Object} clause The query clause.
*/
Condition.prototype.init = function (dataSource, id, clause) {
this._dataSource = dataSource;
this._id = id;
this._query = [clause];
this._started = false;
this._state = [false];
this._satisfied = false;
// Set this to true by default for faster performance
this.earlyExit(true);
};
// Tell ForerunnerDB about our new module
Shared.addModule('Condition', Condition);
// Mixin some commonly used methods
Shared.mixin(Condition.prototype, 'Mixin.Common');
Shared.mixin(Condition.prototype, 'Mixin.ChainReactor');
Shared.synthesize(Condition.prototype, 'id');
Shared.synthesize(Condition.prototype, 'then');
Shared.synthesize(Condition.prototype, 'else');
Shared.synthesize(Condition.prototype, 'earlyExit');
Shared.synthesize(Condition.prototype, 'debug');
/**
* Adds a new clause to the condition.
* @param {Object} clause The query clause to add to the condition.
* @returns {Condition}
*/
Condition.prototype.and = function (clause) {
this._query.push(clause);
this._state.push(false);
return this;
};
/**
* Starts the condition so that changes to data will call callback
* methods according to clauses being met.
* @param {*} initialState Initial state of condition.
* @returns {Condition}
*/
Condition.prototype.start = function (initialState) {
if (!this._started) {
var self = this;
if (arguments.length !== 0) {
this._satisfied = initialState;
}
// Resolve the current state
this._updateStates();
self._onChange = function () {
self._updateStates();
};
// Create a chain reactor link to the data source so we start receiving CRUD ops from it
this._dataSource.on('change', self._onChange);
this._started = true;
}
return this;
};
/**
* Updates the internal status of all the clauses against the underlying
* data source.
* @private
*/
Condition.prototype._updateStates = function () {
var satisfied = true,
i;
for (i = 0; i < this._query.length; i++) {
this._state[i] = this._dataSource.count(this._query[i]) > 0;
if (this._debug) {
console.log(this.logIdentifier() + ' Evaluating', this._query[i], '=', this._query[i]);
}
if (!this._state[i]) {
satisfied = false;
// Early exit since we have found a state that is not true
if (this._earlyExit) {
break;
}
}
}
if (this._satisfied !== satisfied) {
// Our state has changed, fire the relevant operation
if (satisfied) {
// Fire the "then" operation
if (this._then) {
this._then();
}
} else {
// Fire the "else" operation
if (this._else) {
this._else();
}
}
this._satisfied = satisfied;
}
};
/**
* Stops the condition so that callbacks will no longer fire.
* @returns {Condition}
*/
Condition.prototype.stop = function () {
if (this._started) {
this._dataSource.off('change', this._onChange);
delete this._onChange;
this._started = false;
}
return this;
};
/**
* Drops the condition and removes it from memory.
* @returns {Condition}
*/
Condition.prototype.drop = function () {
this.stop();
delete this._dataSource.when[this._id];
return this;
};
// Tell ForerunnerDB that our module has finished loading
Shared.finishModule('Condition');
module.exports = Condition;</code></pre>
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