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[];

    cols: Column[];

    constructor(private carService: CarService) { }

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

        this.cols = [
            {field: 'vin', header: 'Vin', editable: true},
            {field: 'brand', header: 'Brand', editable: true},
            {field: 'year', header: 'Year', editable: true},
            {field: 'color', header: 'Color', editable: true}
        ];
    }
}


<p-dataTable [value]="cars" [columns]="cols" editable="true"></p-dataTable>