Represents a data map for use with a column's dataMap property.
Data maps provide the grid with automatic look up capabilities. For example, you may want to display a customer name instead of his ID, or a color name instead of its RGB value.
The code below binds a grid to a collection of products, then assigns a DataMap to the grid's 'CategoryID' column so the grid displays the category names rather than the raw IDs.
The grid takes advantage of data maps also for editing. If the wijmo.input module is loaded, then when editing data-mapped columns the grid will show a drop-down list containing the values on the map.
```typescript import { FlexGrid, Column } from '@grapecity/wijmo.grid';
// bind grid to products let flex = new FlexGrid({ itemsSource: products });
// map CategoryID column to show category name instead of ID let col = flex.getColumn('CategoryID'); col.dataMap = new DataMap(categories, 'CategoryID', 'CategoryName'); ```
In general, data maps apply to whole columns. However, there are situations where you may want to restrict the options available for a cell based on a value on a different column. For example, if you have "Country" and "City" columns, you will probably want to restrict the cities based on the current country.
There are two ways you can implement these "dynamic" data maps:
In some cases, you may want to create a DataMap to represent an enumeration. This can be done with the following code:
```typescript // build a DataMap for a given enum function getDataMap(enumClass) { let pairs = []; for (let key in enumClass) { var val = parseInt(key); if (!isNaN(val)) { pairs.push({ key: val, name: enumClass[val] }); } } return new DataMap(pairs, 'key', 'name'); } ``` DataMap can treat keys in two different ways, this functionality is controlled by the serializeKeys property. By default, key values are converted to strings before processing, that is different values will produce the same key value if their string representations are equal. This is usually the preferred behavior. You maw need to change this mode if your keys are complex objects or arrays of complex objects. See the serializeKeys property documentation for more details.
constructor(itemsSource: any, selectedValuePath?: string, displayMemberPath?: string): DataMap
Initializes a new instance of the DataMap class.
An array or ICollectionView that contains the items to map.
The name of the property that contains the keys (data values).
The name of the property to use as the visual representation of the items.
Gets the name of the property to use as the visual representation of the item.
Gets or sets a value that indicates whether users should be allowed to enter values that are not present on the DataMap.
In order for a DataMap to be editable, the selectedValuePath and displayMemberPath must be set to the same value.
Gets the name of the property to use as a key for the item (data value).
Gets or sets a value indicating whether key values are converted to strings before use.
The default value is true.
This property is set to true by default, which means that for example the keys 123 (number) and ‘123’ (string), two Date objects defining the same date/time, and two different arrays of primitive values (like [1,2,3]), are treated as the equal key pairs and mapped to the same value.
If to set this property to false, the keys equality will be determined as in the native Map class, that is using the triple-equality (===) operator. This mode is useful if your keys are objects or arrays of objects. Note that in this case DataMap uses the native browser’s Map implementation. Some old mobile browsers, as well as IE9/10, don’t implement the Map interface. In this case DataMap will use its own array based implementation, which can bring serious performance penalties in case of big data arrays.
getDataItem(key: K): V
Gets the item that corresponds to a given key.
The key of the item to retrieve.
getDisplayValue(key: K): string
Gets the display value that corresponds to a given key.
The key of the item to retrieve.
getDisplayValues(dataItem?: V): string[]
Gets an array with all of the display values on the map.
Data item for which to get the display items. This parameter is optional. If not provided, all possible display values should be returned.
getKeyValue(displayValue: string, html?: boolean): K
Gets the key that corresponds to a given display value.
The display value of the item to retrieve.
Whether to convert the lookup values from HTML to plain text.
getKeyValues(): K[]
Gets an array with all of the keys on the map.
onMapChanged(e?: EventArgs): void
Raises the mapChanged event.