[Ionic] Data Model and Observables

Posted on | In , |

The content of this page are summarized from Mark Newman’s lecture notes.

Data Model

A data model is something that:

  • Does not have a UI
  • Represents an Entity within the system, including data and operations

For example, for Tour of Heroes:

  • Hero:
    • Name
    • Powers
    • functions to retrieve and modify these
  • HeroManager
    • The list of Heroes
    • functions to retrieve and modify these

Manager Pattern is a class that curates (creates, provides access, deletes) a collection.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
export class Hero {
    private heroName: string;
    private heroId: number;
    private heroPowers: string[];

    public constructor(private heroName: string,
                        private heroId: number,
                        private heroPowers: string[] = []) {

    }

    public setName(newName: string): void {
        this.heroName = newName;
    }

    public getName(): string {
        return this.heroName;
    }

    public getId(): number {
        return this.heroId;
    }

    public getPowers(): string[] {
        return this.heroPowers;
    }

    public setPowers(newPowers: string[]): void {
        this.heroPowers = newPowers;
    }

    public addPower(newPower: string): void {
        this.heroPowers.push(newPower);
    }

    public removePower(powerToRemove: string) : void {
        if (this.heroPowers.indexOf(powerToRemove) != -1) {
            this.heroPowers.splice(this.heroPowers.indexOf(powerToRemove), 1);
        }
    }

    public toString() : string {
        return this.heroName + "(" + this.heroId + ") " + this.heroPowers;
    }
}
  • HeroManager Model
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53

import { Hero } from './hero';

var nextHeroId: number = 100;

export class HeroManager {

    private heroes: Object = {};

    public constructor() {

    }

    public createHero(heroName: string, heroPowers: string[] = []) {
        let heroId = this.getNextHeroId();
        let hero = new Hero(heroName, heroId, heroPowers);
        this.heroes[heroId] = hero;
    }

    private getNextHeroId(): number {
        return nextHeroId++;
    }

    public getHeroById(id: number): Hero {
        return this.heroes[id];
    }

    public getHeroByName(name: string): Hero {
        let heroList = this.getHeroes();
        for (let i in heroList) {
            if (heroList[i].getName() === name) {
                return heroList[i];
            }
        }
        return undefined;
    }

    public getHeroes(): Hero[] {
        let heroesList: Hero[] = [];
        for (let key in this.heroes) {
            heroesList.push(this.heroes[key]);
        }
        return heroesList;
    }

    public removeHero(hero: Hero) {
        delete this.heroes[hero.getId()];
    }

    public removeHeroById(id: number) {
        delete this.heroes[id];
    }
}