How do I chain "SelectMany" calls with linqjs (or flatten JSON)

Question

Using linq.js how can I chain two SelectMany calls together.

Given the following JSON structure:

[
    {
        "UpFrontCost": "29.95",
        "Currency": "USDAUD",
        "FittingDate": "2013-07-08 06:30:16Z",
        "Widgets": [
            {
                "ID": 3,
                "Name": "Test1"
            },
            {
                "ID": 4,
                "Name": "Test19"
            },
            {
                "ID": 6,
                "Name": "Test8"
            }
        ]
    },
    {
        "UpFrontCost": "29.95",
        "Currency": "USDAUD",
        "FittingDate": "2013-07-08 06:30:16Z",
        "Widgets": [
            {
                "ID": 67,
                "Name": "Test1"
            },
            {
                "ID": 99,
                "Name": "Test19"
            },
            {
                "ID": 34,
                "Name": "Test8"
            }
        ]
    }
]

I would like a list of all the "Widgets" (in this example a list of 6 widgets).

Answer 1

You don't need to really chain anything. Your root object is an array, you just want to select each widget for each object in that array.

var query = Enumerable.From(jsonObject)
    .SelectMany("$.Widgets") // Select each widget found in the Widgets property
    .ToArray();

---

To flatten that array of widgets attaching each property of the parent object to the result, there's a couple of ways you could do it. You can use a nested query using the function syntax.

var query = Enumerable.From(jsonObject)
    .SelectMany(function (item) {
        return Enumerable.From(item.Widgets)
            .Select(function (widget) {
                return {
                    ID: widget.ID,
                    Name: widget.Name,
                    UpFrontCost: item.UpFrontCost,
                    Currency: item.Currency,
                    FittingDate: item.FittingDate
                };
            });
    })
    .ToArray();

Or using the lambda string syntax:

var query = Enumerable.From(items)
    .SelectMany("$.Widgets",
        // argument 1 ($) - the parent object
        // argument 2 ($$) - the selected object (a widget)
        "{ ID: $$.ID, Name: $$.Name, UpFrontCost: $.UpFrontCost, Currency: $.Currency, FittingDate: $.FittingDate }"
    )
    .ToArray();