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DataReader
  JsonReader

Class Ext.data.JsonReader

Package:Ext.data
Defined In:JsonReader.js
Class:JsonReader
Subclasses:ArrayReader
Extends:DataReader

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', mapping: 'firstname'},
        // 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:

  • any of the configuration options for this class
  • a fields property which the JsonReader will use as an argument to the data Record create method in order to configure the layout of the Records it will produce.
  • a sortInfo property which the JsonReader will use to set the Ext.data.Store's sortInfo property
  • any custom properties needed

Config Options

Config OptionsDefined By
 idProperty : String
[id] Name of the property within a row object that contains a record identifier value. Defaults to id
JsonReader
 messageProperty : String
[undefined] Optional name of a property within a server-response that represents a user-feedback message.
DataReader

Public Properties

PropertyDefined By
 buildExtractors : Object
Abstract method, overridden in DataReader extensions such as Ext.data.JsonReader and Ext.data.XmlReader
DataReader
 extractValues : Object
Abstract method overridden in DataReader extensions such as Ext.data.JsonReader and Ext.data.XmlReader
DataReader
 getId : Object
Abstract method created in extension's buildExtractors impl.
DataReader
 getMessage : Object
Abstract method created in extension's buildExtractors impl.
DataReader
 getRoot : Object
Abstract method created in extension's buildExtractors impl.
DataReader
 getSuccess : Object
Abstract method created in extension's buildExtractors impl.
DataReader
 getTotal : Object
Abstract method created in extension's buildExtractors impl.
DataReader
 meta : Mixed
This JsonReader's metadata as passed to the constructor, or as passed in the last data packet's metaData property.
JsonReader

Public Methods

MethodDefined By

Public Events

This class has no public events.