Now, let's create a TodoService class that acts as a service repository to manage todo items. The following is the code snippet of the todo.service.ts file:

import { Todo } from './todo'    
export class TodoService {   
    todos: Array<Todo>   
    constructor() {   
        this.todos = [new Todo('First   item'),   
        new Todo('Second item'),   
        new Todo('Third item')];   
    }   
    getPending() {   
        return   this.todos.filter((todo: Todo) => todo.completed === 
        false);   
    }   
    getCompleted() {   
        return   this.todos.filter((todo: Todo) => todo.completed === 
        true);   
    }   
    remove(todo: Todo) {   
          this.todos.splice(this.todos.indexOf(todo), 1);   
    }   
   
    add(title: string) {   
        this.todos.push(new   Todo(title));   
    }   
    toggleCompletion(todo: Todo)   {   
        todo.completed =   !todo.completed;   
    }   
    removeCompleted() {   
        this.todos =   this.getPending();   
    }   
}

We have created the TodoService class with various methods to add, remove, and return the collection of todo items.