DataTable Incell editing is enabled by setting editable property true both on datatable and columns, when a cell is clicked edit mode is activated, clicking outside of cell or hitting the enter key switches back to view mode after updating the value.

export class DataTableEditableDemo implements OnInit {

    cars: Car[];

    constructor(private carService: CarService) { }

    ngOnInit() {
        this.carService.getCarsSmall().then(cars => this.cars = cars);
    }
}


<p-dataTable [value]="cars" [editable]="true">
    <p-column field="vin" header="Vin" [editable]="true"></p-column>
    <p-column field="year" header="Year" [editable]="true"></p-column>
    <p-column field="brand" header="Brand" [editable]="true"></p-column>
    <p-column field="color" header="Color" [editable]="true"></p-column>
</p-dataTable>