130 lines
13 KiB
JavaScript
130 lines
13 KiB
JavaScript
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(function () {
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/* Imports */
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var Meteor = Package.meteor.Meteor;
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var Tracker = Package.tracker.Tracker;
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var Deps = Package.tracker.Deps;
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/* Package-scope variables */
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var ReactiveVar;
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(function () {
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//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// //
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// packages/reactive-var/reactive-var.js //
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// //
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//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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//
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/* // 1
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* ## [new] ReactiveVar(initialValue, [equalsFunc]) // 2
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* // 3
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* A ReactiveVar holds a single value that can be get and set, // 4
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* such that calling `set` will invalidate any Computations that // 5
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* called `get`, according to the usual contract for reactive // 6
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* data sources. // 7
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* // 8
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* A ReactiveVar is much like a Session variable -- compare `foo.get()` // 9
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* to `Session.get("foo")` -- but it doesn't have a global name and isn't // 10
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* automatically migrated across hot code pushes. Also, while Session // 11
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* variables can only hold JSON or EJSON, ReactiveVars can hold any value. // 12
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* // 13
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* An important property of ReactiveVars, which is sometimes the reason // 14
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* to use one, is that setting the value to the same value as before has // 15
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* no effect, meaning ReactiveVars can be used to absorb extra // 16
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* invalidations that wouldn't serve a purpose. However, by default, // 17
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* ReactiveVars are extremely conservative about what changes they // 18
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* absorb. Calling `set` with an object argument will *always* trigger // 19
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* invalidations, because even if the new value is `===` the old value, // 20
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* the object may have been mutated. You can change the default behavior // 21
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* by passing a function of two arguments, `oldValue` and `newValue`, // 22
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* to the constructor as `equalsFunc`. // 23
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* // 24
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* This class is extremely basic right now, but the idea is to evolve // 25
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* it into the ReactiveVar of Geoff's Lickable Forms proposal. // 26
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*/ // 27
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// 28
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/** // 29
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* @class // 30
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* @instanceName reactiveVar // 31
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* @summary Constructor for a ReactiveVar, which represents a single reactive variable. // 32
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* @locus Client // 33
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* @param {Any} initialValue The initial value to set. `equalsFunc` is ignored when setting the initial value. // 34
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* @param {Function} [equalsFunc] Optional. A function of two arguments, called on the old value and the new value whenever the ReactiveVar is set. If it returns true, no set is performed. If omitted, the default `equalsFunc` returns true if its arguments are `===` and are of type number, boolean, string, undefined, or null.
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*/ // 36
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ReactiveVar = function (initialValue, equalsFunc) { // 37
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if (! (this instanceof ReactiveVar)) // 38
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// called without `new` // 39
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return new ReactiveVar(initialValue, equalsFunc); // 40
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// 41
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this.curValue = initialValue; // 42
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this.equalsFunc = equalsFunc; // 43
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this.dep = new Tracker.Dependency; // 44
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}; // 45
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// 46
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ReactiveVar._isEqual = function (oldValue, newValue) { // 47
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var a = oldValue, b = newValue; // 48
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// Two values are "equal" here if they are `===` and are // 49
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// number, boolean, string, undefined, or null. // 50
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if (a !== b) // 51
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return false; // 52
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else // 53
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return ((!a) || (typeof a === 'number') || (typeof a === 'boolean') || // 54
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(typeof a === 'string')); // 55
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}; // 56
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// 57
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/** // 58
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* @summary Returns the current value of the ReactiveVar, establishing a reactive dependency. // 59
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* @locus Client // 60
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*/ // 61
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ReactiveVar.prototype.get = function () { // 62
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if (Tracker.active) // 63
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this.dep.depend(); // 64
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// 65
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return this.curValue; // 66
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}; // 67
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// 68
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/** // 69
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* @summary Sets the current value of the ReactiveVar, invalidating the Computations that called `get` if `newValue` is different from the old value.
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* @locus Client // 71
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* @param {Any} newValue // 72
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*/ // 73
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ReactiveVar.prototype.set = function (newValue) { // 74
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var oldValue = this.curValue; // 75
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// 76
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if ((this.equalsFunc || ReactiveVar._isEqual)(oldValue, newValue)) // 77
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// value is same as last time // 78
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return; // 79
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// 80
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this.curValue = newValue; // 81
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this.dep.changed(); // 82
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}; // 83
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// 84
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ReactiveVar.prototype.toString = function () { // 85
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return 'ReactiveVar{' + this.get() + '}'; // 86
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}; // 87
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// 88
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ReactiveVar.prototype._numListeners = function() { // 89
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// Tests want to know. // 90
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// Accesses a private field of Tracker.Dependency. // 91
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var count = 0; // 92
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for (var id in this.dep._dependentsById) // 93
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count++; // 94
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return count; // 95
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}; // 96
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// 97
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//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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}).call(this);
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/* Exports */
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if (typeof Package === 'undefined') Package = {};
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Package['reactive-var'] = {
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ReactiveVar: ReactiveVar
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};
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})();
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//# sourceMappingURL=reactive-var.js.map
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