Paging, Sorting and Filtering

The RESTful API created by Remult supports server-side paging, sorting, and filtering. Let's use that to limit, sort and filter the list of tasks.

Limit Number of Fetched Tasks

Since our database may eventually contain a lot of tasks, it make sense to use a paging strategy to limit the number of tasks retrieved in a single fetch from the back-end database.

Let's limit the number of fetched tasks to 20.

In the ngOnInit method, pass an options argument to the find method call and set its limit property to 20.

// src/app/todo/todo.component.ts

ngOnInit() {
  this.taskRepo.find({
    limit: 20
  }).then((items) => (this.tasks = items));
}

There aren't enough tasks in the database for this change to have an immediate effect, but it will have one later on when we'll add more tasks.

TIP

To query subsequent pages, use the Repository.find() method's page option.

Sorting By Creation Date

We would like old tasks to appear first in the list, and new tasks to appear last. Let's sort the tasks by their createdAt field.

In the ngOnInit method, set the orderBy property of the find method call's option argument to an object that contains the fields you want to sort by. Use "asc" and "desc" to determine the sort order.

// src/app/todo/todo.component.ts

ngOnInit() {
  this.taskRepo.find({
    limit: 20,
    orderBy: { createdAt:"asc" }
  }).then((items) => (this.tasks = items));
}

Server side Filtering

Remult supports sending filter rules to the server to query only the tasks that we need.

Adjust the ngOnInit method to fetch only completed tasks.

// src/app/todo/todo.component.ts

ngOnInit() {
  this.taskRepo.find({
    limit: 20,
    orderBy: { createdAt:"asc" },
    where: { completed: true }
  }).then((items) => (this.tasks = items));
}

Note

Because the completed field is of type boolean, the argument is compile-time checked to be of the boolean type. Settings the completed filter to undefined causes it to be ignored by Remult.

Play with different filtering values, and eventually comment it out, since we do need all the tasks

ngOnInit() {
  this.taskRepo.find({
    limit: 20,
    orderBy: { createdAt:"asc" },
    //where: { completed: true }
  }).then((items) => (this.tasks = items));
}

Learn more

Explore the reference for a comprehensive list of filtering options.