/**
* @author Ed Spencer
* @class Ext.data.reader.Json
* @extends Ext.data.reader.Reader
*
* <p>The JSON Reader is used by a Proxy to read a server response that is sent back in JSON format. This usually
* happens as a result of loading a Store - for example we might create something like this:</p>
*
<pre><code>
Ext.define('User', {
extend: 'Ext.data.Model',
fields: ['id', 'name', 'email']
});
var store = Ext.create('Ext.data.Store', {
model: 'User',
proxy: {
type: 'ajax',
url : 'users.json',
reader: {
type: 'json'
}
}
});
</code></pre>
*
* <p>The example above creates a 'User' model. Models are explained in the {@link Ext.data.Model Model} docs if you're
* not already familiar with them.</p>
*
* <p>We created the simplest type of JSON Reader possible by simply telling our {@link Ext.data.Store Store}'s
* {@link Ext.data.proxy.Proxy Proxy} that we want a JSON Reader. The Store automatically passes the configured model to the
* Store, so it is as if we passed this instead:
*
<pre><code>
reader: {
type : 'json',
model: 'User'
}
</code></pre>
*
* <p>The reader we set up is ready to read data from our server - at the moment it will accept a response like this:</p>
*
<pre><code>
[
{
"id": 1,
"name": "Ed Spencer",
"email": "[email protected]"
},
{
"id": 2,
"name": "Abe Elias",
"email": "[email protected]"
}
]
</code></pre>
*
* <p><u>Reading other JSON formats</u></p>
*
* <p>If you already have your JSON format defined and it doesn't look quite like what we have above, you can usually
* pass JsonReader a couple of configuration options to make it parse your format. For example, we can use the
* {@link #root} configuration to parse data that comes back like this:</p>
*
<pre><code>
{
"users": [
{
"id": 1,
"name": "Ed Spencer",
"email": "[email protected]"
},
{
"id": 2,
"name": "Abe Elias",
"email": "[email protected]"
}
]
}
</code></pre>
*
* <p>To parse this we just pass in a {@link #root} configuration that matches the 'users' above:</p>
*
<pre><code>
reader: {
type: 'json',
root: 'users'
}
</code></pre>
*
* <p>Sometimes the JSON structure is even more complicated. Document databases like CouchDB often provide metadata
* around each record inside a nested structure like this:</p>
*
<pre><code>
{
"total": 122,
"offset": 0,
"users": [
{
"id": "ed-spencer-1",
"value": 1,
"user": {
"id": 1,
"name": "Ed Spencer",
"email": "[email protected]"
}
}
]
}
</code></pre>
*
* <p>In the case above the record data is nested an additional level inside the "users" array as each "user" item has
* additional metadata surrounding it ('id' and 'value' in this case). To parse data out of each "user" item in the
* JSON above we need to specify the {@link #record} configuration like this:</p>
*
<pre><code>
reader: {
type : 'json',
root : 'users',
record: 'user'
}
</code></pre>
*
* <p><u>Response metadata</u></p>
*
* <p>The server can return additional data in its response, such as the {@link #totalProperty total number of records}
* and the {@link #successProperty success status of the response}. These are typically included in the JSON response
* like this:</p>
*
<pre><code>
{
"total": 100,
"success": true,
"users": [
{
"id": 1,
"name": "Ed Spencer",
"email": "[email protected]"
}
]
}
</code></pre>
*
* <p>If these properties are present in the JSON response they can be parsed out by the JsonReader and used by the
* Store that loaded it. We can set up the names of these properties by specifying a final pair of configuration
* options:</p>
*
<pre><code>
reader: {
type : 'json',
root : 'users',
totalProperty : 'total',
successProperty: 'success'
}
</code></pre>
*
* <p>These final options are not necessary to make the Reader work, but can be useful when the server needs to report
* an error or if it needs to indicate that there is a lot of data available of which only a subset is currently being
* returned.</p>
*/
Ext.define('Ext.data.reader.Json', {
extend: 'Ext.data.reader.Reader',
alternateClassName: 'Ext.data.JsonReader',
alias : 'reader.json',
root: '',
/**
* @cfg {String} record The optional location within the JSON response that the record data itself can be found at.
* See the JsonReader intro docs for more details. This is not often needed.
*/
/**
* @cfg {Boolean} useSimpleAccessors True to ensure that field names/mappings are treated as literals when
* reading values. Defalts to <tt>false</tt>.
* For example, by default, using the mapping "foo.bar.baz" will try and read a property foo from the root, then a property bar
* from foo, then a property baz from bar. Setting the simple accessors to true will read the property with the name
* "foo.bar.baz" direct from the root object.
*/
useSimpleAccessors: false,
/**
* Reads a JSON object and returns a ResultSet. Uses the internal getTotal and getSuccess extractors to
* retrieve meta data from the response, and extractData to turn the JSON data into model instances.
* @param {Object} data The raw JSON data
* @return {Ext.data.ResultSet} A ResultSet containing model instances and meta data about the results
*/
readRecords: function(data) {
//this has to be before the call to super because we use the meta data in the superclass readRecords
if (data.metaData) {
this.onMetaChange(data.metaData);
}
/**
* @deprecated will be removed in Ext JS 5.0. This is just a copy of this.rawData - use that instead
* @property {Object} jsonData
*/
this.jsonData = data;
return this.callParent([data]);
},
//inherit docs
getResponseData: function(response) {
var data;
try {
data = Ext.decode(response.responseText);
}
catch (ex) {
Ext.Error.raise({
response: response,
json: response.responseText,
parseError: ex,
msg: 'Unable to parse the JSON returned by the server: ' + ex.toString()
});
}
//<debug>
if (!data) {
Ext.Error.raise('JSON object not found');
}
//</debug>
return data;
},
buildExtractors : function() {
var me = this;
me.callParent(arguments);
if (me.root) {
me.getRoot = me.createAccessor(me.root);
} else {
me.getRoot = function(root) {
return root;
};
}
},
* @private
* We're just preparing the data for the superclass by pulling out the record objects we want. If a {@link #record}
* was specified we have to pull those out of the larger JSON object, which is most of what this function is doing
* @param {Object} root The JSON root node
* @return {Ext.data.Model[]} The records
*/
extractData: function(root) {
var recordName = this.record,
data = [],
length, i;
if (recordName) {
length = root.length;
if (!length && Ext.isObject(root)) {
length = 1;
root = [root];
}
for (i = 0; i < length; i++) {
data[i] = root[i][recordName];
}
} else {
data = root;
}
return this.callParent([data]);
},
/**
* @private
* Returns an accessor function for the given property string. Gives support for properties such as the following:
* 'someProperty'
* 'some.property'
* 'some["property"]'
* This is used by buildExtractors to create optimized extractor functions when casting raw data into model instances.
*/
createAccessor: function() {
var re = /[\[\.]/;
return function(expr) {
if (Ext.isEmpty(expr)) {
return Ext.emptyFn;
}
if (Ext.isFunction(expr)) {
return expr;
}
if (this.useSimpleAccessors !== true) {
var i = String(expr).search(re);
if (i >= 0) {
return Ext.functionFactory('obj', 'return obj' + (i > 0 ? '.' : '') + expr);
}
}
return function(obj) {
return obj[expr];
};
};
}()
});