module Ext_data_reader_Reader: sig .. end

Readers are used to interpret data to be loaded into a Model instance or a Store - often in response to an AJAX request. In general there is usually no need to create a Reader instance directly, since a Reader is almost always used together with a Proxy, and is configured using the Proxy's reader configuration property:

Ext.create('Ext.data.Store', {
    model: 'User',
    proxy: {
        type: 'ajax',
        url : 'users.json',
        reader: {
            type: 'json',
            root: 'users'
        }
    },
});

The above reader is configured to consume a JSON string that looks something like this:

{
    "success": true,
    "users": [
        { "name": "User 1" },
        { "name": "User 2" }
    ]
}

Loading Nested Data

Readers have the ability to automatically load deeply-nested data objects based on the associations configured on each Model. Below is an example demonstrating the flexibility of these associations in a fictional CRM system which manages a User, their Orders, OrderItems and Products. First we'll define the models:

Ext.define("User", {
    extend: 'Ext.data.Model',
    fields: [
        'id', 'name'
    ],

    hasMany: {model: 'Order', name: 'orders'},

    proxy: {
        type: 'rest',
        url : 'users.json',
        reader: {
            type: 'json',
            root: 'users'
        }
    }
});

Ext.define("Order", {
    extend: 'Ext.data.Model',
    fields: [
        'id', 'total'
    ],

    hasMany  : {model: 'OrderItem', name: 'orderItems', associationKey: 'order_items'},
    belongsTo: 'User'
});

Ext.define("OrderItem", {
    extend: 'Ext.data.Model',
    fields: [
        'id', 'price', 'quantity', 'order_id', 'product_id'
    ],

    belongsTo: ['Order', {model: 'Product', associationKey: 'product'}]
});

Ext.define("Product", {
    extend: 'Ext.data.Model',
    fields: [
        'id', 'name'
    ],

    hasMany: 'OrderItem'
});

This may be a lot to take in - basically a User has many Orders, each of which is composed of several OrderItems. Finally, each OrderItem has a single Product. This allows us to consume data like this:

{
    "users": [
        {
            "id": 123,
            "name": "Ed",
            "orders": [
                {
                    "id": 50,
                    "total": 100,
                    "order_items": [
                        {
                            "id"      : 20,
                            "price"   : 40,
                            "quantity": 2,
                            "product" : {
                                "id": 1000,
                                "name": "MacBook Pro"
                            }
                        },
                        {
                            "id"      : 21,
                            "price"   : 20,
                            "quantity": 3,
                            "product" : {
                                "id": 1001,
                                "name": "iPhone"
                            }
                        }
                    ]
                }
            ]
        }
    ]
}

The JSON response is deeply nested - it returns all Users (in this case just 1 for simplicity's sake), all of the Orders for each User (again just 1 in this case), all of the OrderItems for each Order (2 order items in this case), and finally the Product associated with each OrderItem. Now we can read the data and use it as follows:

var store = Ext.create('Ext.data.Store', {
    model: "User"
});

store.load({
    callback: function() {
        //the user that was loaded
        var user = store.first();

        console.log("Orders for " + user.get('name') + ":")

        //iterate over the Orders for each User
        user.orders().each(function(order) {
            console.log("Order ID: " + order.getId() + ", which contains items:");

            //iterate over the OrderItems for each Order
            order.orderItems().each(function(orderItem) {
                //we know that the Product data is already loaded, so we can use the synchronous getProduct
                //usually, we would use the asynchronous version (see Ext.data.association.BelongsTo)
                var product = orderItem.getProduct();

                console.log(orderItem.get('quantity') + ' orders of ' + product.get('name'));
            });
        });
    }
});

Running the code above results in the following:

Orders for Ed:
Order ID: 50, which contains items:
2 orders of MacBook Pro
3 orders of iPhone

class type t = object .. end

class type configs = object .. end

class type events = object .. end

class type statics = object .. end

val of_configs : configs Js.t -> t Js.t

val to_configs : t Js.t -> configs Js.t