Data binding in Angular Treeview component
27 Apr 202415 minutes to read
The TreeView component provides the option to load data either from local data sources or from remote data services.
This can be done through dataSource property that is a member of the fields property.
The dataSource property supports array of JavaScript objects and DataManager.
It also supports different kinds of data services such as OData, OData V4, Web API, URL, and JSON with the help of DataManager adaptors.
TreeView has load on demand (Lazy load), by default. It reduces the bandwidth size when consuming huge data.
It loads first level nodes initially, and when parent node is expanded, loads the child nodes based on the parentID/child member.
By default, the loadOnDemand is set to true. By disabling this property, all the tree nodes are rendered at the beginning itself.
You can use the dataBound event to perform actions.
This event will be triggered once the data source is populated in the TreeView.
Local data
To bind local data to the TreeView, you can assign a JavaScript object array to the dataSource property.
The TreeView component requires three fields (id, text, and parentID) to render local data source.
When mapper fields are not specified, it takes the default values as the mapping fields. Local data source can also be
provided as an instance of the DataManager. It supports two kinds of local data binding methods.
-
Hierarchical data
-
Self-referential data
Hierarchical data
TreeView can be populated with hierarchical data source that contains nested array of JSON objects.
You can directly assign hierarchical data to the dataSource property, and map all the field members with corresponding keys from the hierarchical data to fields property.
In the following example, code, name, and countries columns from hierarchical data have been mapped to id, child, and text fields, respectively.
import { NgModule } from '@angular/core'
import { BrowserModule } from '@angular/platform-browser'
import { FormsModule } from '@angular/forms'
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations'
import { Component } from '@angular/core';
@Component({
imports: [
FormsModule,TreeViewModule
],
standalone: true,
selector: 'app-container',
template: `<div id='treeparent'><ejs-treeview id='treeelement' [fields]='field'></ejs-treeview></div>`
})
export class AppComponent {
constructor() {
}
//define the data source
public continents:Object[] = [
{
code: 'AF', name: 'Africa', countries: [
{ code: 'NGA', name: 'Nigeria' },
{ code: 'EGY', name: 'Egypt' },
{ code: 'ZAF', name: 'South Africa' }
]
},
{
code: 'AS', name: 'Asia', expanded: true, countries: [
{ code: 'CHN', name: 'China' },
{ code: 'IND', name: 'India', selected: true },
{ code: 'JPN', name: 'Japan' }
]
},
{
code: 'EU', name: 'Europe', countries: [
{ code: 'DNK', name: 'Denmark' },
{ code: 'FIN', name: 'Finland' },
{ code: 'AUT', name: 'Austria' }
]
},
{
code: 'NA', name: 'North America', countries: [
{ code: 'USA', name: 'United States of America' },
{ code: 'CUB', name: 'Cuba' },
{ code: 'MEX', name: 'Mexico' }
]
},
{
code: 'SA', name: 'South America', countries: [
{ code: 'BRA', name: 'Brazil' },
{ code: 'COL', name: 'Colombia' },
{ code: 'ARG', name: 'Argentina' }
]
},
{
code: 'OC', name: 'Oceania', countries: [
{ code: 'AUS', name: 'Australia' },
{ code: 'NZL', name: 'New Zealand' },
{ code: 'WSM', name: 'Samoa' }
]
},
{
code: 'AN', name: 'Antarctica', countries: [
{ code: 'BVT', name: 'Bouvet Island' },
{ code: 'ATF', name: 'French Southern Lands' }
]
}
];
public field:Object = { dataSource: this.continents, id: 'code', text: 'name', child: 'countries' };
}import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));Self-referential Data
TreeView can be populated from self-referential data structure that contains array of JSON objects with parentID mapping.
You can directly assign self-referential data to the dataSource property, and map all the field members with corresponding keys from self-referential data to fields property.
In the following example, id, pid, hasChild, and name columns from self-referential data have been mapped to id, parentID, hasChildren, and text fields, respectively.
import { NgModule } from '@angular/core'
import { BrowserModule } from '@angular/platform-browser'
import { FormsModule } from '@angular/forms'
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations'
import { Component } from '@angular/core';
@Component({
imports: [
FormsModule,TreeViewModule
],
standalone: true,
selector: 'app-container',
// specifies the template string for the TreeView component with fields property
template: `<div id='treeparent'><ejs-treeview id='treeelement' [fields]='field'></ejs-treeview></div>`
})
export class AppComponent {
constructor() {
}
// defined the array of data
public localData: Object[] = [
{ id: 1, name: 'Discover Music', hasChild: true, expanded: true },
{ id: 2, pid: 1, name: 'Hot Singles' },
{ id: 3, pid: 1, name: 'Rising Artists' },
{ id: 4, pid: 1, name: 'Live Music' },
{ id: 7, name: 'Sales and Events', hasChild: true },
{ id: 8, pid: 7, name: '100 Albums - $5 Each' },
{ id: 9, pid: 7, name: 'Hip-Hop and R&B Sale' },
{ id: 10, pid: 7, name: 'CD Deals' },
{ id: 11, name: 'Categories', hasChild: true },
{ id: 12, pid: 11, name: 'Songs' },
{ id: 13, pid: 11, name: 'Bestselling Albums' },
{ id: 14, pid: 11, name: 'New Releases' },
{ id: 15, pid: 11, name: 'Bestselling Songs' },
{ id: 16, name: 'MP3 Albums', hasChild: true },
{ id: 17, pid: 16, name: 'Rock' },
{ id: 18, pid: 16, name: 'Gospel' },
{ id: 19, pid: 16, name: 'Latin Music' },
{ id: 20, pid: 16, name: 'Jazz' },
{ id: 21, name: 'More in Music', hasChild: true },
{ id: 22, pid: 21, name: 'Music Trade-In' },
{ id: 23, pid: 21, name: 'Redeem a Gift Card' },
{ id: 24, pid: 21, name: 'Band T-Shirts' }
];
// maps the appropriate column to fields property
public field: Object = { dataSource: this.localData, id: 'id', parentID: 'pid', text: 'name', hasChildren: 'hasChild' };
}import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));Remote data
TreeView can also be populated from a remote data service with the help of DataManager component
and Query property.
It supports different kinds of data services such as OData, OData V4, Web API, URL, and JSON with the help of DataManager adaptors.
You can assign service data as an instance of DataManager to the dataSource property. To interact with remote data source, you have to provide the endpoint url.
The DataManager that acts as an interface between the service endpoint and the TreeView requires the following information to interact with service endpoint properly.
-
DataManager->url: Defines the service endpoint to fetch data. -
DataManager->adaptor: Defines the adaptor option. By default, ODataAdaptor is used for remote binding.
Adaptor is responsible for processing response and request from/to the service endpoint. The @syncfusion/ej2-data package provides some predefined adaptors designed to interact with service endpoints. They are,
-
UrlAdaptor: Used to interact with remote services. This is the base adaptor for all remote based adaptors. -
ODataAdaptor: Used to interact with OData endpoints. -
ODataV4Adaptor: Used to interact with OData V4 endpoints. -
WebApiAdaptor: Used to interact with Web API created under OData standards. -
WebMethodAdaptor: Used to interact with web methods.
In the following example, ODataV4Adaptor is used to fetch data from remote services. The EmployeeID, FirstName, and Title columns from Employees table have been mapped to id, text, and hasChildren fields respectively for first level nodes.
The OrderID, EmployeeID, and ShipName columns from orders table have been mapped to id, parentID, and text fields respectively for second level nodes.
import { NgModule } from '@angular/core'
import { BrowserModule } from '@angular/platform-browser'
import { FormsModule } from '@angular/forms'
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations'
import { Component } from '@angular/core';
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data'
@Component({
imports: [
FormsModule,TreeViewModule
],
standalone: true,
selector: 'app-container',
// specifies the template string for the TreeView component with remote dataSource
template: `<div id='treeparent'><ejs-treeview id='treeelement' [fields]='field'></ejs-treeview></div>`
})
export class AppComponent {
constructor() {
}
//bind the DataManager instance to dataSource property
public data: Object = new DataManager({
url: 'https://services.odata.org/V4/Northwind/Northwind.svc',
adaptor: new ODataV4Adaptor,
crossDomain: true,
});
//bind the Query instance to query property
public query:Object = new Query().from('Employees').select('EmployeeID,FirstName,Title').take(5);
public query1:Object = new Query().from('Orders').select('OrderID,EmployeeID,ShipName').take(5);
//Map the fields
public field:Object ={ dataSource: this.data, query: this.query, id: 'EmployeeID', text: 'FirstName', hasChildren: 'EmployeeID', tooltip: 'Title',
child: { dataSource: this.data, query: this.query1, id: 'OrderID', parentID: 'EmployeeID', text: 'ShipName' }
};
}import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));