cours-420-301-ah/json-gnome-exemple.ipynb

In [2]:

class Human {

    constructor(name, age){
        this.name = name;
        this.age = age;
    }
    
    toJSON(){
        return {
            type: "Human",
            age: this.age,
            name: this.name,
        }
    }
}

class Gnome{
    constructor(name, height){
        this.name = name;
        this.height = height;
    }

    toJSON(){
        return {
            type: "Gnome",
            name: this.name,
            height: this.height,
        }
    }
}

Objectif, sérialiser une liste de gnome ou d'human

In [6]:

const persons = [
    new Human("Boutros", 89),
    new Human("Fares", 12),
    new Gnome("Petit Pied", 102),
    new Gnome("Grand Gaillard", 135),
]


function serializePersons(persons){
    const personObjets = persons.map(person => person.toJSON())
    localStorage.setItem("persons.json", JSON.stringify(personObjets));
}

serializePersons(persons)

Le statue de local storage est donc...

In [7]:

console.log(localStorage.getItem("persons.json"))

[{"type":"Human","age":89,"name":"Boutros"},{"type":"Human","age":12,"name":"Fares"},{"type":"Gnome","name":"Petit Pied","height":102},{"type":"Gnome","name":"Grand Gaillard","height":135}]

Plus bas, il s'agit de la logique pour deserialiser les personnes

In [22]:

function deserializeHumanObject(humanObject){
    return new Human(humanObject.name, humanObject.age)
}

function deserializeGnomeObject(gnomeObject){
    return new Gnome(gnomeObject.name, gnomeObject.height)
}

function deserializePersonObject(person){
    if(person.type === "Human"){
        return deserializeHumanObject(person);
    }
    if(person.type === "Gnome"){
        return deserializeGnomeObject(person);
    }
}


function deserializePersons(){
    const personObjects = JSON.parse(localStorage.getItem("persons.json"));
    if(!personObjects){
        return []; // le cas ou il n'y a rien de sauvegarder dans "persons.json"
    }
    return personObjects.map(deserializePersonObject)
}

Plus bas, voici comment deserialiser toutes les personnes du localstorage

In [20]:

deserializePersons()

Out [20]:

[]

Cas special: deserializer un constenue de localstorage vide

In [21]:

localStorage.clear() // efface tout du localstorage.  Le cas du premier visiteur
deserializePersons()

Out [21]:

[]