Task dependency or task relationship can be established between two tasks in Gantt. This dependency affects the project schedule. If you change the predecessor of a task, it will affect the successor task, which will affect the next task, and so on. Relationship can be established between parent-parent tasks, child-child tasks, parent-child and child-parent task.
Task relationships are categorized into four types based on the start and finish dates of the task.
You cannot start a task until the dependent task also starts.
You cannot finish a task until the dependent task is started.
You cannot start a task until the dependent task is completed.
You cannot finish a task until the dependent task is completed.
Task relationship is defined in the data source as a string value, and this value is mapped to the Gantt component by using the taskFields.dependency
property. The following code example demonstrates how to enable the predecessor in the Gantt component.
let data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Predecessor: "2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0, Predecessor: "6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent } from '@syncfusion/ej2-react-gantt';
class App extends React.Component {
constructor() {
super(...arguments);
this.taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} height='450px'>
</GanttComponent>;
}
}
;
ReactDOM.render(<App />, document.getElementById('root'));
<!DOCTYPE html>
<html lang="en">
<head>
<title>Syncfusion React Gantt</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Essential JS 2 for React Components" />
<meta name="author" content="Syncfusion" />
<link href="https://cdn.syncfusion.com/ej2/20.4.38/material.css" rel="stylesheet" type="text/css"/>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
<script src="systemjs.config.js"></script>
<style>
#loader {
color: #008cff;
height: 40px;
left: 45%;
position: absolute;
top: 45%;
width: 30%;
}
</style>
</head>
<body>
<div id='root'>
<div id='loader'>Loading....</div>
</div>
</body>
</html>
let data: Object[] = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4,Predecessor:"2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0,Predecessor:"6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent } from '@syncfusion/ej2-react-gantt';
class App extends React.Component<{}, {}>{
public taskFields: any = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} height = '450px'>
</GanttComponent>
}
};
ReactDOM.render(<App />, document.getElementById('root'));
In the Gantt component, the predecessor offset can be defined with the following duration units:
You can define an offset with various offset duration units for predecessors by using the following code example.
let data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/04/2019'), Duration: 4, Predecessor: "2FS+2days", Progress: 50 },
{ TaskID: 5, TaskName: 'Clear the building site', StartDate: new Date('04/04/2019'), Duration: 2, Progress: 30, Predecessor: '4FF+960m' }
]
},
{
TaskID: 6,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 7, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 9, TaskName: 'Estimation approval', StartDate: new Date('04/06/2019'), Duration: 0, Predecessor: "7SS+16h", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent } from '@syncfusion/ej2-react-gantt';
class App extends React.Component {
constructor() {
super(...arguments);
this.taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} height='450px'>
</GanttComponent>;
}
}
;
ReactDOM.render(<App />, document.getElementById('root'));
<!DOCTYPE html>
<html lang="en">
<head>
<title>Syncfusion React Gantt</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Essential JS 2 for React Components" />
<meta name="author" content="Syncfusion" />
<link href="https://cdn.syncfusion.com/ej2/20.4.38/material.css" rel="stylesheet" type="text/css"/>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
<script src="systemjs.config.js"></script>
<style>
#loader {
color: #008cff;
height: 40px;
left: 45%;
position: absolute;
top: 45%;
width: 30%;
}
</style>
</head>
<body>
<div id='root'>
<div id='loader'>Loading....</div>
</div>
</body>
</html>
let data: Object[] = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/04/2019'), Duration: 4,Predecessor:"2FS+2days", Progress: 50 },
{ TaskID: 5, TaskName: 'Clear the building site', StartDate: new Date('04/04/2019'), Duration: 2, Progress: 30, Predecessor: '4FF+960m'}
]
},
{
TaskID: 6,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 7, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 9, TaskName: 'Estimation approval', StartDate: new Date('04/06/2019'), Duration: 0,Predecessor:"7SS+16h", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent } from '@syncfusion/ej2-react-gantt';
class App extends React.Component<{}, {}>{
public taskFields: any = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} height = '450px'>
</GanttComponent>
}
};
ReactDOM.render(<App />, document.getElementById('root'));
In Gantt, task relationship link can be broken by editing the start date, end date and duration value of task. When the task relationship broken on any edit action. This can be handled in Gantt in two ways.
When the task relationship link is broken on any edit action, then the actionBegin
event will be triggered with requestType
argument as validateLinkedTask
. You can validate the editing action within the actionBegin event using the validateMode
event argument. The validateMode
event argument has the following properties:
Argument | Default value | Description |
---|---|---|
args.validateMode.respectLink | false | In this validation mode, the predecessor links get high priority. With this mode enabled, when the successor task is moved before the predecessor task’s end date, the editing will be reverted, and dates will be validated based on the dependency links. |
args.validateMode.removeLink | false | In this validation mode, the taskbar editing gets high priority. For inappropriate task dates, the dependency links will be removed and tasks will be moved to the edited date. |
args.validateMode.preserveLinkWithEditing | true | In this validation mode, the taskbar editing will be considered along with the dependency links. This relationship will be maintained by updating the offset value of predecessors. |
By default, the preserveLinkWithEditing
validation mode will be enabled, so the predecessors are updated with offset values.
The following sample explains enabling the respectLink
validation mode while editing the linked tasks in the actionBegin
event.
let data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Predecessor: "2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0, Predecessor: "6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent, Inject, Edit } from '@syncfusion/ej2-react-gantt';
class App extends React.Component {
constructor() {
super(...arguments);
this.taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks',
};
this.editOptions = {
allowEditing: true,
allowTaskbarEditing: true
};
}
actionBegin(args) {
if (args.requestType == "validateLinkedTask") {
args.validateMode.respectLink = true;
}
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} editSettings={this.editOptions} actionBegin={this.actionBegin.bind(this)} height='450px'>
<Inject services={[Edit]}/>
</GanttComponent>;
}
}
;
ReactDOM.render(<App />, document.getElementById('root'));
<!DOCTYPE html>
<html lang="en">
<head>
<title>Syncfusion React Gantt</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Essential JS 2 for React Components" />
<meta name="author" content="Syncfusion" />
<link href="https://cdn.syncfusion.com/ej2/20.4.38/material.css" rel="stylesheet" type="text/css"/>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
<script src="systemjs.config.js"></script>
<style>
#loader {
color: #008cff;
height: 40px;
left: 45%;
position: absolute;
top: 45%;
width: 30%;
}
</style>
</head>
<body>
<div id='root'>
<div id='loader'>Loading....</div>
</div>
</body>
</html>
let data: Object[] = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4,Predecessor:"2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0,Predecessor:"6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent, Inject, Edit, EditSettingsModel } from '@syncfusion/ej2-react-gantt';
class App extends React.Component<{}, {}>{
public taskFields: any = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks',
};
public editOptions: EditSettingsModel = {
allowEditing: true,
allowTaskbarEditing:true
};
actionBegin (args: any) {
if (args.requestType == "validateLinkedTask") {
args.validateMode.respectLink = true;
}
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields}
editSettings={this.editOptions} actionBegin={this.actionBegin.bind(this)} height = '450px'>
<Inject services={[Edit]} />
</GanttComponent>
}
};
ReactDOM.render(<App />, document.getElementById('root'));
When disabling all the validation modes in the actionBegin
event, a validation pop-up will be displayed prompting users to select the validation mode to validate taskbar editing.
This validation pop-up will display different options based on the successor task’s start date after editing.
If you move the successor task that starts after the predecessor task’s end date, then a dialog will be rendered with the following options:
If you move the successor task that starts before the predecessor task’s end date, then a dialog will be rendered with the following options:
The following code example shows how to enable the predecessor validation dialog in Gantt.
let data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Predecessor: "2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0, Predecessor: "6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent, Inject, Edit } from '@syncfusion/ej2-react-gantt';
class App extends React.Component {
constructor() {
super(...arguments);
this.taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
this.editOptions = {
allowEditing: true,
allowTaskbarEditing: true
};
}
actionBegin(args) {
if (args.requestType == "validateLinkedTask") {
args.validateMode.preserveLinkWithEditing = false;
}
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields} editSettings={this.editOptions} actionBegin={this.actionBegin.bind(this)} height='450px'>
<Inject services={[Edit]}/>
</GanttComponent>;
}
}
;
ReactDOM.render(<App />, document.getElementById('root'));
<!DOCTYPE html>
<html lang="en">
<head>
<title>Syncfusion React Gantt</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Essential JS 2 for React Components" />
<meta name="author" content="Syncfusion" />
<link href="https://cdn.syncfusion.com/ej2/20.4.38/material.css" rel="stylesheet" type="text/css"/>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
<script src="systemjs.config.js"></script>
<style>
#loader {
color: #008cff;
height: 40px;
left: 45%;
position: absolute;
top: 45%;
width: 30%;
}
</style>
</head>
<body>
<div id='root'>
<div id='loader'>Loading....</div>
</div>
</body>
</html>
let data: Object[] = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 0, Progress: 50 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4,Predecessor:"2FS", Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 0,Predecessor:"6SS", Progress: 50 }
]
},
];
import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { GanttComponent, Inject, Edit, EditSettingsModel } from '@syncfusion/ej2-react-gantt';
class App extends React.Component<{}, {}>{
public taskFields: any = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
public editOptions: EditSettingsModel = {
allowEditing: true,
allowTaskbarEditing:true
};
actionBegin (args: any) {
if (args.requestType == "validateLinkedTask") {
args.validateMode.preserveLinkWithEditing = false;
}
}
render() {
return <GanttComponent dataSource={data} taskFields={this.taskFields}
editSettings={this.editOptions} actionBegin={this.actionBegin.bind(this)} height = '450px'>
<Inject services={[Edit]} />
</GanttComponent>
}
};
ReactDOM.render(<App />, document.getElementById('root'));