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# Example: DataSource.Function

DataSource.Function allows the implementer to define a JavaScript function that returns data values, for maximum customizeability. A DataSchema plugin is used to normalize incoming data into a known format for consistency of usage by other components.

#### Array

###### Data

    [
        {name:"abc",id:123},
        {name:"def",id:456},
        {name:"ghi",id:789}
    ]

###### Schema

    {
        resultFields: ["name","id"]
    }

###### Normalized data

#### JSON

###### Data

    {
        "profile":{
            "current":160,
            "target":150
        },
        "reference": [
            {
                "category":"exercise",
                "type":"expenditure",
                "activities":[
                    {"name":"biking", "calories":550},
                    {"name":"golf", "calories":1000},
                    {"name":"running", "calories":650},
                    {"name":"swimming", "calories":650},
                    {"name":"walking", "calories":225}
                ]
            },
            {
                "category":"nutrition",
                "type":"intake",
                "fruit":[
                    {"name":"apple", "calories":70},
                    {"name":"banana", "calories":70},
                    {"name":"orange", "calories":90},
                ],
                "vegetables":[
                    {"name":"baked potato", "calories":150},
                    {"name":"broccoli", "calories":50},
                    {"name":"green beans", "calories":30}
                ]
            }
        ],
        "program": [
            {
                "category":"exercise",
                "schedule":[
                    {"day":"sunday", "activity":"swimming"},
                    {"day":"monday", "activity":"running"},
                    {"day":"tuesday", "activity":"biking"},
                    {"day":"wednesday", "activity":"running"},
                    {"day":"thursday", "activity":"swimming"},
                    {"day":"friday", "activity":"running"},
                    {"day":"saturday", "activity":"golf"}
                ]
            },
            {
                "category":"diet",
                "schedule":[
                ]
            }
        ]
    }

###### Schema

    {
        resultListLocator: "reference[1].fruit",
        resultFields: ["name","calories"]
    }

###### Normalized data

Your custom function can return arbitrary data, so use the appropriate schema plugin to normalize the data into a consistent format. Array data would use a DataSourceArraySchema plugin:

    YUI().use("datasource-function", "datasource-arrayschema", function(Y) {
        var myFunction = function(request) {
            return [
                {name:"abc",id:123},
                {name:"def",id:456},
                {name:"ghi",id:789}
            ];
        },
        myDataSource = new Y.DataSource.Function({source:myFunction}),
        myCallback = {
            success: function(e){
                alert(e.response);
            },
            failure: function(e){
                alert("Could not retrieve data: " + e.error.message);
            }
        };

        myDataSource.plug(Y.Plugin.DataSourceArraySchema, {
            schema: {
                resultFields: ["name","id"]
            }
        });

        myDataSource.sendRequest({callback:myCallback});
    });

Whereas JSON data would use a DataSourceJSONSchema plugin:

    YUI().use("datasource-function", "datasource-jsonschema", function(Y) {
        var myFunction = function(request) {
            return {
                "profile":{
                    "current":160,
                    "target":150
                },
                "reference": [
                    {
                        ...
                    },
                    {
                        "category":"nutrition",
                        "type":"intake",
                        "fruit":[
                            {"name":"apple", "calories":70},
                            {"name":"banana", "calories":70},
                            {"name":"orange", "calories":90},
                        ],
                        "vegetables":[
                            {"name":"baked potato", "calories":150},
                            {"name":"broccoli", "calories":50},
                            {"name":"green beans", "calories":30}
                        ]
                    }
                ],
                "program": [
                    ...
                ]
            };
        },
        myDataSource = new Y.DataSource.Function({source:myFunction}),
        myCallback = {
            success: function(e){
                alert(e.response);
            },
            failure: function(e){
                alert("Could not retrieve data: " + e.error.message);
            }
        };

        myDataSource.plug(Y.Plugin.DataSourceJSONSchema, {
            schema: {
                resultListLocator: "reference[1].fruit",
                resultFields: ["name","calories"]
            }
        });

        myDataSource.sendRequest({callback:myCallback});
    });