Class Ext.data.JsonReader

Data reader class to create an Array of Ext.data.Record objects from a JSON response based on mappings in a provided Ext.data.Record constructor.

Example code:

var Employee = Ext.data.Record.create([
    {name: 'firstname'},                  // map the Record's "firstname" field to the row object's key of the same name
    {name: 'job', mapping: 'occupation'}  // map the Record's "job" field to the row object's "occupation" key
]);
var myReader = new Ext.data.JsonReader(
    {                             // The metadata property, with configuration options:
        totalProperty: "results", //   the property which contains the total dataset size (optional)
        root: "rows",             //   the property which contains an Array of record data objects
        idProperty: "id"          //   the property within each row object that provides an ID for the record (optional)
    },
    Employee  // Ext.data.Record constructor that provides mapping for JSON object
);

This would consume a JSON data object of the form:

{
    results: 2,  // Reader's configured totalProperty
    rows: [      // Reader's configured root
        { id: 1, firstname: 'Bill', occupation: 'Gardener' },         // a row object
        { id: 2, firstname: 'Ben' , occupation: 'Horticulturalist' }  // another row object
    ]
}

Automatic configuration using metaData

It is possible to change a JsonReader's metadata at any time by including a metaData property in the JSON data object. If the JSON data object has a metaData property, a Store object using this Reader will reconfigure itself to use the newly provided field definition and fire its metachange event. The metachange event handler may interrogate the metaData property to perform any configuration required. Note that reconfiguring a Store potentially invalidates objects which may refer to Fields or Records which no longer exist.

The metaData property in the JSON data object may contain:

To use this facility to send the same data as the example above (without having to code the creation of the Record constructor), you would create the JsonReader like this:

var myReader = new Ext.data.JsonReader();

The first data packet from the server would configure the reader by containing a metaData property and the data. For example, the JSON data object might take the form:

{
    metaData: {
        idProperty: 'id',
        root: 'rows',
        totalProperty: 'results',
        fields: [
            {name: 'name'},
            {name: 'job', mapping: 'occupation'}
        ],
        sortInfo: {field: 'name', direction:'ASC'}, // used by store to set its sortInfo
        foo: 'bar' // custom property
    },
    results: 2,
    rows: [ // an Array
        { 'id': 1, 'name': 'Bill', occupation: 'Gardener' },
        { 'id': 2, 'name': 'Ben', occupation: 'Horticulturalist' }
    ]
}