Class Ext.data.JsonReader

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

Example code:

var myReader = new Ext.data.JsonReader({
    // metadata configuration options:
    idProperty: 'id'
    root: 'rows',
    totalProperty: 'results',
    Ext.data.DataReader.messageProperty: "msg"  // The element within the response that provides a user-feedback message (optional)

    // the fields config option will internally create an Ext.data.Record
    // constructor that provides mapping for reading the record data objects
    fields: [
        // map Record's 'firstname' field to data object's key of same name
        {name: 'name'},
        // map Record's 'job' field to data object's 'occupation' key
        {name: 'job', mapping: 'occupation'}
    ]
});

This would consume a JSON data object of the form:

{
    results: 2000, // Reader's configured totalProperty
    rows: [        // Reader's configured root
        // record data objects:
        { id: 1, firstname: 'Bill', occupation: 'Gardener' },
        { id: 2, firstname: 'Ben' , occupation: 'Horticulturalist' },
        ...
    ]
}

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.

To use this facility 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"
        "successProperty": "success",
        "fields": [
            {"name": "name"},
            {"name": "job", "mapping": "occupation"}
        ],
        // used by store to set its sortInfo
        "sortInfo":{
           "field": "name",
           "direction": "ASC"
        },
        // paging data (if applicable)
        "start": 0,
        "limit": 2,
        // custom property
        "foo": "bar"
    },
    // Reader's configured successProperty
    "success": true,
    // Reader's configured totalProperty
    "results": 2000,
    // Reader's configured root
    // (this data simulates 2 results per page)
    "rows": [ // *Note: this must be an Array
        { "id": 1, "name": "Bill", "occupation": "Gardener" },
        { "id": 2, "name":  "Ben", "occupation": "Horticulturalist" }
    ]
}

The metaData property in the JSON data object should contain: