Class Ext.data.JsonReader

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 "job" field to the row object's "occupation" key
]);
var myReader = new Ext.data.JsonReader({
    totalProperty: "results",             // The property which contains the total dataset size (optional)
    root: "rows",                         // The property which contains an Array of row objects
    id: "id"                              // The property within each row object that provides an ID for the record (optional)
}, Employee);

This would consume a JSON object of the form:

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

It is possible to change a JsonReader's metadata at any time by including a metaData property in the data object. If this is detected in the object, a Store object using this Reader will reconfigure itself to use the newly provided field definition and fire its metachange event. In undergoing this change, the Store sets its sortInfo property from the sortInfo property in the new metadata. Note that reconfiguring a Store potentially invalidates objects which may refer to Fields or Records which no longer exist.

The metaData property may contain any of the configuration options for this class. Additionally, it may contain a fields property which the JsonReader will use as an argument to Ext.data.Record.create to configure the layout of the Records which it will produce.

Using the metaData property, and the Store's metachange event, it is possible to have a Store-driven control initialize itself. The metachange event handler may interrogate the metaData property (which may contain any user-defined properties needed) and the metaData.fields property to perform any configuration required.

To use this facility to send the same data as the above example 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 as well as the data:

{
    metaData: {
        totalProperty: 'results',
        root: 'rows',
        id: 'id',
        fields: [
            {name: 'name'},
            {name: 'occupation'}
        ]
    },
    results: 2,
    rows: [
        { 'id': 1, 'name': 'Bill', occupation: 'Gardener' },
        { 'id': 2, 'name': 'Ben', occupation: 'Horticulturalist' }
    ]
}