Custom Sources.md

Custom data access logic can be implemented using the CustomStore class. A developer should implement all data access operations in the CustomStore.

<!--JavaScript-->
var myStore = new DevExpress.data.CustomStore({
    load: function(loadOptions) {
        // . . .
    },
    byKey: function(key, extra) {
        // . . .
    },
    update: function(values) {
        // . . .
    },
    . . .  
});

var dataSource = new DevExpress.data.DataSource({
    store: myStore
});

The DataSource supports a more brief syntax without introducing an explicit CustomStore instance.

<!--JavaScript-->
var dataSource = new DevExpress.data.DataSource({
    load: function(loadOptions) {
        // . . .
    },
    byKey: function(key, extra) {
        // . . .
    },
    update: function(values) {
        // . . .
    },
    . . .
});

For example, the following synthetic implementation generates an infinite read-only list:

<!--JavaScript-->
var infiniteListSource = new DevExpress.data.DataSource({
    load: function(loadOptions) {
        var result = [ ];
        for(var i = 0; i < loadOptions.take; i++)
            result.push({ id: 1 + loadOptions.skip + i });            
        return result;
    },
    byKey: function(key) {
        return { id: key };
    }
});

In this example, load and byKey functions are synchronous, that is why they instantly return a result.

[note] DevExtreme also provides store implementations for the BreezeJS and JayData data libraries. You can use them as a reference if you decide to introduce a custom store implementation for another data library.