/**
* @author Ed Spencer
*
* 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:
*
* 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'
* }
* }
* });
*
* 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.
*
* 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:
*
* reader: {
* type : 'json',
* model: 'User'
* }
*
* The reader we set up is ready to read data from our server - at the moment it will accept a response like this:
*
* [
* {
* "id": 1,
* "name": "Ed Spencer",
* "email": "[email protected]"
* },
* {
* "id": 2,
* "name": "Abe Elias",
* "email": "[email protected]"
* }
* ]
*
* ## Reading other JSON formats
*
* 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 #cfg-root} configuration to parse data that comes back like this:
*
* {
* "users": [
* {
* "id": 1,
* "name": "Ed Spencer",
* "email": "[email protected]"
* },
* {
* "id": 2,
* "name": "Abe Elias",
* "email": "[email protected]"
* }
* ]
* }
*
* To parse this we just pass in a {@link #root} configuration that matches the 'users' above:
*
* reader: {
* type: 'json',
* root: 'users'
* }
*
* Sometimes the JSON structure is even more complicated. Document databases like CouchDB often provide metadata
* around each record inside a nested structure like this:
*
* {
* "total": 122,
* "offset": 0,
* "users": [
* {
* "id": "ed-spencer-1",
* "value": 1,
* "user": {
* "id": 1,
* "name": "Ed Spencer",
* "email": "[email protected]"
* }
* }
* ]
* }
*
* 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:
*
* reader: {
* type : 'json',
* root : 'users',
* record: 'user'
* }
*
* ## Response MetaData
*
* The server can return metadata in its response, in addition to the record data, that describe attributes
* of the data set itself or are used to reconfigure the Reader. To pass metadata in the response you simply
* add a `metaData` attribute to the root of the response data. The metaData attribute can contain anything,
* but supports a specific set of properties that are handled by the Reader if they are present:
*
* - {@link #root}: the property name of the root response node containing the record data
* - {@link #idProperty}: property name for the primary key field of the data
* - {@link #totalProperty}: property name for the total number of records in the data
* - {@link #successProperty}: property name for the success status of the response
* - {@link #messageProperty}: property name for an optional response message
* - {@link Ext.data.Model#cfg-fields fields}: Config used to reconfigure the Model's fields before converting the
* response data into records
*
* An initial Reader configuration containing all of these properties might look like this ("fields" would be
* included in the Model definition, not shown):
*
* reader: {
* type : 'json',
* root : 'root',
* idProperty : 'id',
* totalProperty : 'total',
* successProperty: 'success',
* messageProperty: 'message'
* }
*
* If you were to pass a response object containing attributes different from those initially defined above, you could
* use the `metaData` attribute to reconifgure the Reader on the fly. For example:
*
* {
* "count": 1,
* "ok": true,
* "msg": "Users found",
* "users": [{
* "userId": 123,
* "name": "Ed Spencer",
* "email": "[email protected]"
* }],
* "metaData": {
* "root": "users",
* "idProperty": 'userId',
* "totalProperty": 'count',
* "successProperty": 'ok',
* "messageProperty": 'msg'
* }
* }
*
* You can also place any other arbitrary data you need into the `metaData` attribute which will be ignored by the Reader,
* but will be accessible via the Reader's {@link #metaData} property (which is also passed to listeners via the Proxy's
* {@link Ext.data.proxy.Proxy#metachange metachange} event (also relayed by the {@link Ext.data.AbstractStore#metachange
* store}). Application code can then process the passed metadata in any way it chooses.
*
* A simple example for how this can be used would be customizing the fields for a Model that is bound to a grid. By passing
* the `fields` property the Model will be automatically updated by the Reader internally, but that change will not be
* reflected automatically in the grid unless you also update the column configuration. You could do this manually, or you
* could simply pass a standard grid {@link Ext.panel.Table#columns column} config object as part of the `metaData` attribute
* and then pass that along to the grid. Here's a very simple example for how that could be accomplished:
*
* // response format:
* {
* ...
* "metaData": {
* "fields": [
* { "name": "userId", "type": "int" },
* { "name": "name", "type": "string" },
* { "name": "birthday", "type": "date", "dateFormat": "Y-j-m" },
* ],
* "columns": [
* { "text": "User ID", "dataIndex": "userId", "width": 40 },
* { "text": "User Name", "dataIndex": "name", "flex": 1 },
* { "text": "Birthday", "dataIndex": "birthday", "flex": 1, "format": 'Y-j-m', "xtype": "datecolumn" }
* ]
* }
* }
*
* The Reader will automatically read the meta fields config and rebuild the Model based on the new fields, but to handle
* the new column configuration you would need to handle the metadata within the application code. This is done simply enough
* by handling the metachange event on either the store or the proxy, e.g.:
*
* var store = Ext.create('Ext.data.Store', {
* ...
* listeners: {
* 'metachange': function(store, meta) {
* myGrid.reconfigure(store, meta.columns);
* }
* }
* });
*
*/
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 {String} [metaProperty="metaData"]
* Name of the property from which to retrieve the `metaData` attribute. See {@link #metaData}.
*/
metaProperty: 'metaData',
/**
* @cfg {Boolean} useSimpleAccessors True to ensure that field names/mappings are treated as literals when
* reading values.
*
* 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) {
var me = this,
meta;
//this has to be before the call to super because we use the meta data in the superclass readRecords
if (me.getMeta) {
meta = me.getMeta(data);
if (meta) {
me.onMetaChange(meta);
}
} else if (data.metaData) {
me.onMetaChange(data.metaData);
}
/**
* @property {Object} jsonData
* A copy of this.rawData.
* @deprecated Will be removed in Ext JS 5.0. This is just a copy of this.rawData - use that instead.
*/
me.jsonData = data;
return me.callParent([data]);
},
//inherit docs
getResponseData: function(response) {
var data, error;
try {
data = Ext.decode(response.responseText);
return this.readRecords(data);
} catch (ex) {
error = new Ext.data.ResultSet({
total : 0,
count : 0,
records: [],
success: false,
message: ex.message
});
this.fireEvent('exception', this, response, error);
Ext.Logger.warn('Unable to parse the JSON returned by the server');
return error;
}
},
buildExtractors : function() {
var me = this,
metaProp = me.metaProperty;
me.callParent(arguments);
if (me.root) {
me.getRoot = me.createAccessor(me.root);
} else {
me.getRoot = Ext.identityFn;
}
if (metaProp) {
me.getMeta = me.createAccessor(metaProp);
}
},
* @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
* @method
* Returns an accessor function for the given property string. Gives support for properties such as the following:
*
* - 'someProperty'
* - 'some.property'
* - '["someProperty"]'
* - 'values[0]'
*
* This is used by {@link #buildExtractors} to create optimized extractor functions for properties that are looked
* up directly on the source object (e.g. {@link #successProperty}, {@link #messageProperty}, etc.).
*/
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];
};
};
}()),
/**
* @private
* @method
* Returns an accessor expression for the passed Field. Gives support for properties such as the following:
*
* - 'someProperty'
* - 'some.property'
* - '["someProperty"]'
* - 'values[0]'
*
* This is used by {@link #buildRecordDataExtractor} to create optimized extractor expressions when converting raw
* data into model instances. This method is used at the field level to dynamically map values to model fields.
*/
createFieldAccessExpression: (function() {
var re = /[\[\.]/;
return function(field, fieldVarName, dataName) {
var mapping = field.mapping,
hasMap = mapping || mapping === 0,
map = hasMap ? mapping : field.name,
result,
operatorIndex;
// mapping: false means that the Field will never be read from server data.
if (mapping === false) {
return;
}
if (typeof map === 'function') {
result = fieldVarName + '.mapping(' + dataName + ', this)';
} else if (this.useSimpleAccessors === true || ((operatorIndex = String(map).search(re)) < 0)) {
if (!hasMap || isNaN(map)) {
// If we don't provide a mapping, we may have a field name that is numeric
map = '"' + map + '"';
}
result = dataName + "[" + map + "]";
} else if (operatorIndex === 0) {
// If it matched at index 0 then it must be bracket syntax (e.g. ["foo"]). In this case simply
// join the two, e.g. 'field["foo"]':
result = dataName + map;
} else {
// If it matched at index > 0 it must be either dot syntax (e.g. field.foo) or a values array
// item (e.g. values[0]). For the latter, we can simply concatenate the values reference to
// the source directly like 'field.values[0]'. For dot notation we have to support arbitrary
// levels (field.foo.bar), any of which could be null or undefined, so we have to create the
// returned value such that the references will be assigned defensively in the calling code.
// The output should look like 'field.foo && field.foo.bar' in that case.
var parts = map.split('.'),
len = parts.length,
i = 1,
tempResult = dataName + '.' + parts[0],
buffer = [tempResult]; // for 'field.values[0]' this will be the returned result
for (; i < len; i++) {
tempResult += '.' + parts[i];
buffer.push(tempResult);
}
result = buffer.join(' && ');
}
return result;
};
}())
});