Angular TreeList - columns.lookup
A lookup column restricts the set of values that can be chosen when a user edits or filters the column. In a lookup column, each cell is a drop-down menu. You can use a lookup column when you need to substitute displayed values with required values. For example, consider that you have two arrays of objects: drivers
and buses
.
var drivers = [ { driverID: 1, firstName: "John", lastName: "Smith", busID: 2 }, { driverID: 2, firstName: "Lizzy", lastName: "Cook", busID: 1 }, { driverID: 3, firstName: "Brian", lastName: "Hawkins", busID: 3 } ]; var buses = [ { busID: 1, plates: "123456" }, { busID: 2, plates: "AB-1234" }, { busID: 3, plates: "CD-9876" } ];
All drivers
have the busID
field, which refers to a bus. If drivers
is the main dataSource, the Bus ID column displays bus IDs, which provides little information to a user. It will be more useful to display bus license plates instead of IDs. For this, the buses
array must be set as a lookup dataSource for the Bus ID column. Then, the names of data fields must be assigned to the valueExpr and displayExpr options. Values from the valueExpr data field will be replaced with values from the displayExpr data field.
jQuery
$(function() { $("#treeListContainer").dxTreeList({ dataSource: drivers, // ... columns: [{ dataField: "busID", lookup: { dataSource: buses, valueExpr: "busID", displayExpr: "plates" } }] }); });
Angular
<dx-tree-list [dataSource]="drivers"> <dxi-column dataField="busID"> <dxo-lookup [dataSource]="buses" valueExpr="busID" displayExpr="plates"> </dxo-lookup> </dxi-column> </dx-tree-list>
import { DxTreeListModule } from "devextreme-angular"; // ... export class AppComponent { drivers = [ { driverID: 1, firstName: "John", lastName: "Smith", busID: 2 }, { driverID: 2, firstName: "Lizzy", lastName: "Cook", busID: 1 }, { driverID: 3, firstName: "Brian", lastName: "Hawkins", busID: 3 } ]; buses = [ { busID: 1, plates: "123456" }, { busID: 2, plates: "AB-1234" }, { busID: 3, plates: "CD-9876" } ]; } @NgModule({ imports: [ // ... DxTreeListModule ], // ... })
With this code, the Bus ID column contains license plates instead of IDs. Moreover, the user can choose a plate number from the drop-down menu when editing cells or applying a filter to this column.
See Also
dataSource
This option accepts one of the following:
Array of objects or primitives
A JavaScript array that contains plain objects or primitives.DataSource configuration object
A DataSource configuration object. More information about the DataSource and the DevExtreme Data Layer is available in the Data Layer article.Store instance
An ArrayStore, LocalStore, ODataStore, or CustomStore instance.Function
A function that returns one of the above.
If the lookup data source contains objects, specify the valueExpr and displayExpr options in addition to the dataSource.
See Also
displayExpr
This option accepts a string - the name of the data field that provides displayed values, or a function that returns the displayed value.
Values in a lookup column are sorted by the valueExpr field. Implement the column's calculateSortValue function if you want to sort by the displayExpr field instead:
jQuery
columns: [{ // ... lookup: { // ... }, calculateSortValue: function (data) { var value = this.calculateCellValue(data); return this.lookup.calculateCellValue(value); } }]
Angular
<dxi-column ... [calculateSortValue]="calculateSortValue"> <dxo-lookup ... ></dxo-lookup> </dxi-column>
export class AppComponent { calculateSortValue (data) { let column = this as any; let value = column.calculateCellValue(data); return column.lookup.calculateCellValue(value); } }
valueExpr
Values from this field will be replaced with values from the displayExpr field.
If you have technical questions, please create a support ticket in the DevExpress Support Center.