84 lines
2.4 KiB
JavaScript
84 lines
2.4 KiB
JavaScript
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// A simple module to replace `Backbone.sync` with *localStorage*-based
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// persistence. Models are given GUIDS, and saved into a JSON object. Simple
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// as that.
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// Generate four random hex digits.
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function S4() {
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return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
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};
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// Generate a pseudo-GUID by concatenating random hexadecimal.
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function guid() {
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return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());
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};
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// Our Store is represented by a single JS object in *localStorage*. Create it
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// with a meaningful name, like the name you'd give a table.
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var Store = function(name) {
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this.name = name;
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var store = localStorage.getItem(this.name);
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this.data = (store && JSON.parse(store)) || {};
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};
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_.extend(Store.prototype, {
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// Save the current state of the **Store** to *localStorage*.
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save: function() {
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localStorage.setItem(this.name, JSON.stringify(this.data));
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},
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// Add a model, giving it a (hopefully)-unique GUID, if it doesn't already
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// have an id of it's own.
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create: function(model) {
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if (!model.id) model.id = model.attributes.id = guid();
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this.data[model.id] = model;
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this.save();
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return model;
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},
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// Update a model by replacing its copy in `this.data`.
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update: function(model) {
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this.data[model.id] = model;
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this.save();
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return model;
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},
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// Retrieve a model from `this.data` by id.
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find: function(model) {
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return this.data[model.id];
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},
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// Return the array of all models currently in storage.
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findAll: function() {
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return _.values(this.data);
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},
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// Delete a model from `this.data`, returning it.
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destroy: function(model) {
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delete this.data[model.id];
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this.save();
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return model;
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}
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});
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// Override `Backbone.sync` to use delegate to the model or collection's
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// *localStorage* property, which should be an instance of `Store`.
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Backbone.sync = function(method, model, success, error) {
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var resp;
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var store = model.localStorage || model.collection.localStorage;
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switch (method) {
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case "read": resp = model.id ? store.find(model) : store.findAll(); break;
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case "create": resp = store.create(model); break;
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case "update": resp = store.update(model); break;
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case "delete": resp = store.destroy(model); break;
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}
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if (resp) {
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success(resp);
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} else {
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error("Record not found");
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}
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};
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