Working with the Grid

In this tutorial, you'll learn about the Grid's event system, how to select rows, and how to set up your grid for editing.

  • Difficulty: Intermediate
  • Dojo Version: 1.7

dgrid

This tutorial covers the dojox/grid/DataGrid in depth. Beginning with Dojo 1.7, you should use the dgrid, a next-generation grid component that takes full advantage of modern browsers and object stores. Visit the dgrid site for a collection of dgrid tutorials.

Getting Started

We've learned about the Data Grid and how to populate a Grid with data. Now we'll introduce three major concepts to be used when working with the dojox/grid/DataGrid: how the Grid's event system works, how the Grid's selections work, and how to set up your Grid so that you can edit data.

The Grid's Event System

The Grid supports quite a few events—see the API reference for a full list—but for this tutorial, we are going to focus on the most common event handler used by developers: onRowClick. onRowClick is used to detect clicks on rows (duh!), but the way in which it passes information about the event is special: instead of passing specific arguments like many of the events in the Dijit ecosphere, it augments standard DOM event objects with some custom information.

The decorated event object

When events are fired, the Grid decorates the DOM event object passed to event handlers by the browser. It does this by attaching the following properties to the event object:

  • grid: A reference to the grid in which the event was fired
  • cell: A reference to the specific cell in the grid from which the event was fired
  • rowIndex: A reference to the index of the row in which the event was fired

All of these custom properties are accessible from the event object that is passed to your connected handler. Say, for example, we'd like to get a reference to the underlying dojo/store item that a row represents when it is clicked. Remember that the name of event is the event handler without the "on" prefix, and so when using the new on() event handler, we use the event name of "RowClick" (and widgets allow for all lower case, so we could use "rowclick"), therefore we would do something like this:

		myGrid.on("RowClick", function(evt){
			var idx = evt.rowIndex,
				rowData = grid.getItem(idx);
		
			// display the data from the row (last is last name, first is first name)
			document.getElementById("results").innerHTML =
				"You have clicked on " + rowData.last + ", " + rowData.first + ".";
			}, true);
View Demo

We focus on rows instead of cells for events because a Grid is a representation (or view) of a collection of data items. Since each row represents a single item, it is more logical and efficient to work with full rows instead of attempting to handle individual cells.

Don't forget: when working with a Grid, you should be doing any kind of data operations in the underlying data store and not with the DOM structure of the Grid directly.

Other events

The Grid supports a large set of basic events on both rows and cells, which you can use to create customizations (such as visual alterations) if needed. They are as follows:

Row HeaderCell Cell
onRowClick onHeaderCellClick onCellClick
onRowContextMenu onHeaderCellContextMenu onCellContextMenu
onRowDblClick onHeaderCellDblClick onCellDblClick
onRowFocus onHeaderCellFocus onCellFocus
onRowMouseDown onHeaderCellMouseDown onCellMouseDown
onRowMouseOut onHeaderCellMouseOut onCellMouseOut
onRowMouseOver onHeaderCellMouseOver onCellMouseOver

Each of these events are passed the same decorated DOM event object as we saw in our onRowClick example.

The Grid also supports a number of other events, including notifications when a cell is being edited, and when rows/items are selected. See the API reference for more details.

Row selections with the Grid

The Grid supports the notion of row-based selections, providing several options for selection behavior. The desired behavior can be specified when creating the Grid using the selectionMode property:

require(["dojox/grid/DataGrid"], function(DataGrid){

	var myGrid = new DataGrid({
		store: myStore,
		structure: myStructure,
		selectionMode: "single"
	}, "someNode");
	myGrid.startup();

The possible values for selectionMode are:

  • none: No selections are allowed
  • single: Only one row may be selected at a time; clicking a second row will remove the selection from the first
  • multiple: Each click toggles the selection of the row in question
  • extended: The default mode; normal clicks operate like single, but multiple rows / ranges of rows may be selected by holding modifier keys (e.g. Ctrl and Shift on Windows) while clicking

Row selectors

In addition to selecting rows by clicking directly on data cells, the Grid also provides a few options allowing selection via a dedicated area of each row.

The most basic of these is exposed via the Grid's rowSelector property. This can be set to a CSS-compatible width measurement (e.g. "20px"), or simply to true which will use a default width.

The Grid also provides options for selection via checkboxes, or—in the case of the single row selection mode—radio buttons. These capabilities are exposed via the semi-private custom view types dojox/grid/_CheckBoxSelector and dojox/grid/_RadioSelector. You would include one of these views in your grid structure as follows:

require(["dojox/grid/cells", "dojox/grid/_CheckBoxSelector"], function(gridCells){

	var myStructure = [
		// First, a view using the _CheckBoxSelector custom type.
		// Don't forget to require dojox/grid/_CheckBoxSelector
		{
			type: "dojox.grid._CheckBoxSelector"
		},
		// Now include the data cells in a view occupying the rest of the grid.
		[
			[
				new gridCells.RowIndex({ width: "10%" }),
				{ name: "Column 1", field: "col1", width: "30%" },
				{ name: "Column 2", field: "col2", width: "30%" },
				{ name: "Column 3", field: "col3", width: "30%" }
			],[
				{ name: "Column 4", field: "col4", colSpan: 4 }
			]
		]
	];

You may have noticed we snuck an interesting cell type into this structure: gridCells.RowIndex. This cell simply displays the index of each row in the grid. It is not at all required in order to take advantage of the Grid's selection capabilities, but it may be useful particularly during the process of prototyping a grid structure.

To see these selector features in action, check out the selector demo below.

Getting selections from the Grid

The ability to select data is pointless unless you have some way of retrieving the current selection. The Grid handles this through the selection property, and three event handlers—onSelected, onDeselected, and onSelectionChanged.

When listening to the onSelected or onDeselected handlers, you will receive the index of the row that has been selected or deselected, respectively. Additionally, you can use the Grid's selection property to retrieve the items represented by the selected rows and operate on them, like so:

require(["dojo/_base/array", "dojo/_base/lang"], function(baseArray, lang){
	function reportSelection(node){
		var items = this.selection.getSelected();
		var tmp = baseArray.map(items, function(item){
			return item.id;
		}, this);
		var msg = "You have selected row" + ((tmp.length > 1) ? "s ": " ");
		node.innerHTML = msg + tmp.join(", ");
	}
	// assuming our grid is named myGrid
	myGrid.on("SelectionChanged",
		lang.hitch(grid, reportSelection, document.getElementById("results")), true);
View Demo

The return from selection.getSelected() is always an array, regardless of the selection mode used; i.e. if you set up your Grid to only allow one selection at a time, getSelected will still return an array, with a single item in it.

For more information about the Grid's selection object, take a look at the Selection object in the API reference, where you'll find that you have full programmatic access to grid selection operations.

Now that we have learned how selections work with a Grid, let's take a look at a major piece of functionality: editing data with a Grid.

Editing data with the Grid

Like a typical relational database GUI (Graphical User Interface) or a spreadsheet program, the Grid can also allow you to edit data at the field level. To do this, you have to designate whether a field is editable in your structure definition, and specify what type of editing you want to enable through the use of the type property in each column definition, like so:

	require(["dojox/grid/DataGrid", "dojox/grid/cells", "dojox/grid/cells/dijit",
		"dojo/date/locale", "dojo/currency", "dijit/form/DateTextBox", "dijit/form/CurrencyTextBox",
		"dijit/form/HorizontalSlider", "dojo/domReady!"
	], function(DataGrid, cells, cellsDijit, locale, currency, DateTextBox, CurrencyTextBox, HorizontalSlider){
		function formatCurrency(inDatum){
			return isNaN(inDatum) ? '...' : currency.format(inDatum, this.constraint);
		}
		function formatDate(inDatum){
			return locale.format(new Date(inDatum), this.constraint);
		}
		gridLayout = [{
			defaultCell: { width: 8, editable: true, type: cells._Widget, styles: 'text-align: right;'  },
			cells: [
				{ name: 'Id', field: 'id', editable: false, width: 2 /* Can't edit ID's of dojo/store items */ },
				{ name: 'Date', field: 'col8', width: 10, editable: true,
					widgetClass: DateTextBox,
					formatter: formatDate,
					constraint: {formatLength: 'long', selector: "date"}},
				{ name: 'Priority', styles: 'text-align: center;', field: 'col1', width: 10,
					type: cells.ComboBox,
					options: ["normal","note","important"]},
				{ name: 'Mark', field: 'col2', width: 5, styles: 'text-align: center;',
					type: cells.CheckBox},
				{ name: 'Status', field: 'col3',
					styles: 'text-align: center;',
					type: cells.Select,
					options: ["new", "read", "replied"] },
				{ name: 'Message', field: 'col4', styles: '', width: 10 },
				{ name: 'Amount', field: 'col5', formatter: formatCurrency, constraint: {currency: 'EUR'},
					widgetClass: CurrencyTextBox, width: "auto" },
				{ name: 'Amount', field: 'col5', formatter: formatCurrency, constraint: {currency: 'EUR'},
					widgetClass: HorizontalSlider, width: 10}
			]
		}];
View Demo

Note that when defining a Grid's structure declaratively, cell editor type is specified in the th via the cellType attribute, not type.

By default, if you specify a column to be editable but don't specify a widget constructor, you will get a plain text box. This is often adequate; however, you might find that you'll need to limit the options of entry, deal with dates, or have some other special needs—like in the example above.

We set up our example structure with a defaultCell definition, which sets a baseline of properties to be applied to all cells in our structure, unless explicitly overridden on a per-cell basis. In this case, we specify that we want cells to be editable unless otherwise noted, and set the type to a basic custom editor widget called dojox/grid/cells._Widget, from which all the custom grid-based editing widgets derive. We then customize each column definition to specify which kind of editing widget we'd really like to use in each case.

As you can see, the Grid itself provides a number of "special" widgets for you. In our example, we can see dojox/grid/cells/DateTextBox, dojox/grid/cells/ComboBox, dojox/grid/cells/Select, dojox/grid/cells/Editor, and dojox/grid/cells/CheckBox; we can also see the use of actual Dijits, such as dijit/form/CurrencyTextBox and dijit/form/HorizontalSlider. Using each of these widgets may also require additional properties to be defined; for example, the ComboBox and Select widgets require an additional property called options.

These widgets for editing on a cell-level (all defined within the dojox/grid/cells namespace) have been defined because of the special HTML needs of the Grid. When in doubt about what kind of widget to use for editing, look first to see if the widget in question has been implemented under dojox/grid/cells before trying to use the Dijit equivalent. This is particularly true of any kind of Dijit that defines/uses a popup of some sort.

Because of the data binding that occurs between Dijit-based form widgets and dojo/store via the Grid, this should be all you need to enable editing for a data set.

Another friendly reminder: you will need to use a write-enabled store in order to do any kind of editing within a Grid. Depending on the store, you may also have to do a periodic save() in order to capture any edits within a Grid; this is entirely dependent on the store of choice.

Conclusion

In this tutorial, we've built upon previous topics by introducing additional features of the Grid. The Grid exposes many events to which custom logic can be applied. Several row selection modes are available; the Grid provides APIs for determining selected rows and being notified when a selection occurs. Using the Grid's powerful editing capabilities, it is possible to modify the data set from within the Grid itself.

Armed with this knowledge, you should be well on your way towards creating an application capable of displaying and manipulating information in complex data sets.

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