I have created a small sample demonstrating how your requirement could be achieved by using the Custom Editor Provider feature of igGrid and handling the editCellEnding event of the igGridUpdating feature:

{
    name: "Updating",
    ...
    columnSettings: [
        {
            columnKey: "Category",
            editorProvider: new $.ig.EditorProviderInput()
        }
    ]
}

$.ig.EditorProviderInput = $.ig.EditorProviderInput || $.ig.EditorProvider.extend({
    ...
    setValue: function (val) {
        if (val !== null && typeof val !== 'string') {
            this.editor.element.val(val.Name);
        } else {
            this.editor.element.val(val);
        }
    }
    ...
});

{
    name: "Updating",
    ...
    editCellEnding: function (evt, ui) {
        var record = $("#grid").igGrid("findRecordByKey", ui.rowID);
        if (ui.columnKey === 'Category') {
            if (!ui.rowAdding) {
                ui.value = { ID: record.Category.ID, Name: ui.value }
            } else {
                ui.value = { ID: Date.now() + Math.random(), Name: ui.value }
            }
        }
    }
    ...
}

More information regarding the Custom Editor Provider feature you can find here.

Please test the sample on your side and let me know whether you find it helpful.

Looking forward to hearing from you.

Regards,
Viktor Kombov
Entry Level Software Developer
Infragistics, Inc.

If the value that you are trying to edit is object, you should use an editor that can handle complex object. I believe you will find the Data Grid - Handling Complex Objects sample very helpful. There is demonstrated how you can use the igCombo control as an editor for columns with dataType "object":

// dataSource for the combo editor
var northWindCategoriesJSON = [
    { "ID": 0, "Name": "Food" },
    { "ID": 1, "Name": "Beverages" },
    { "ID": 2, "Name": "Electronics" }
];

$("#grid").igGrid({
    ...
    columns: [
        ...
        {
            headerText: "Category", key: "Category", dataType: "object", mapper: function (record) {
                return record.Category.Name;
            }
        }
    ],
    features: [
        ...
        {
            name: "Updating",
            editMode: "cell",
            columnSettings: [
                {
                    columnKey: "Category",
                    editorType: "combo",
                    editorOptions: {
                        dataSource: northWindCategoriesJSON,
                        textKey: "Name",
                        valueKey: "ID",
                        mode: "dropdown"
                    }
                }
            ]
        }
    ]
});

Additionally, here you can find more detailed information regarding how to handle complex data extraction from complex objects.

Please let me know if you need any further assistance regarding this matter.

Regards,
Viktor Kombov
Entry Level Software Developer
Infragistics, Inc.