Submit Update Form

Chapter Objectives

Handle form submission
Learn how to process form data when updating tasks.
Update task data
Implement the logic to update task information in the service.
Navigate after update
Learn how to redirect users after successful task updates.

Update the Task with TaskService

The TaskService already includes a function to add a new task to the list. Let’s add a new function to update an existing task in the list.

Update the file src/app/task-service.ts.

import { Injectable, signal, WritableSignal } from "@angular/core";
import { Task } from "./task.model";

@Injectable({
  providedIn: "root",
})
export class TaskService {
  tasks: WritableSignal<Task[]> = signal([
    {
      title: "Task 1",
      description: "Description of task 1",
      createdAt: new Date(),
    },
    {
      title: "Task 2",
      description: "Description of task 2",
      createdAt: new Date(),
    },
  ]);

  addTask(task: Task) {
    this.tasks.update((tasks) => {
     return [...tasks, {
      ...task,
      createdAt: new Date(),
    });
  }

  getTask(id: string) {
    return this.tasks().find((task) => task.id === id);
  }

  updateTask(task: Task) {
    this.tasks.update((tasks) => {
     return tasks.map((t) => t.id === task.id ? task : t);
    });
  }
}

Update the TaskFormComponent

The TaskFormComponent is currently used to add a new task to the list.

Handle the update action through the form without creating a new task. To do this, keep the same submit function but update it to use the updateTask function from the TaskService.

When?

If the task has an id, call the updateTask function.
If the task doesn’t have an id, call the addTask function.

submit() {
    const id = this.route.snapshot.paramMap.get('id');

    if (id) {
      const existingTask = this.taskService.getTask(id);
      this.taskService.updateTask({
        ...existingTask,
        ...this.task
      });
    } else {
      this.taskService.addTask(this.task);
    }
    this.router.navigate(['/']);
  }

In both cases, return to the task list.

Update the file src/app/task-form/task-form.ts.

import { Component, OnInit } from "@angular/core";
import { ActivatedRoute } from "@angular/router";
import { TaskService } from "../task.service";
import { Task } from "../task.model";

@Component({
  selector: "app-task-form",
  templateUrl: "./task-form.component.html",
  styleUrls: ["./task-form.component.css"],
})
export class TaskFormComponent implements OnInit {
  private taskService = inject(TaskService);
  private router = inject(Router);
  private route = inject(ActivatedRoute);

  taskForm = new FormGroup({
    title: new FormControl('', [Validators.required]),
    description: new FormControl('', [Validators.required])
  });

  ngOnInit() {
    const id = this.route.snapshot.paramMap.get("id");
    if (id) {
      const task = this.taskService.getTask(id);
      this.taskForm.patchValue(task);
    }
  }

  submit() {
    const id = this.route.snapshot.paramMap.get("id");

    if (id) {
      const existingTask = this.taskService.getTask(id);
      this.taskService.updateTask({
        ...existingTask,
        ...this.task,
      });
    } else {
      this.taskService.addTask(this.task);
    }
    this.router.navigate(["/"]);
  }
}

Test it

Click the Update button next to a task in the list.
Update the form with the new task details.
Click the Update Task button.
The task should be updated in the list.

What you've learned

In this chapter, you learned how to update the TaskFormComponent to handle both updating and creating tasks.