How to cast all nodes of a nested JSON tree to instances of a class in angular 2 Typescript?

Question

I have a class named Leaf, and I'd like to make all nodes of a json response instances of Leaf. The json response looks like this:

JSON Response

{
    "name":"animal",
    "state":false,
    "children":[
        {
            "name":"cats",
            "state":false,
            "children":[
                {
                    "name":"tiger",
                    "state":false,
                },
                {
                    "name":"puma",
                    "state":false,
                    "children":[
                        {
                            "name":"babyPuma",
                            "state":true
                        }
                    ]
                }
            ]
        },
        {
            "name":"dogs",
            "state":false,
            "children":[
                {
                    "name":"pitbull",
                    "state":true
                },
                {
                    "name":"german",
                    "state":false,
                    "children":[
                        {
                            "name":"shepherd",
                            "state":true
                        }
                    ]
                }
            ]
        }
    ]
}

I am getting the response using observable and have learned to cast the first node:

http.service.ts snippet

getTreeData(): Observable<Leaf>{  
    var headers = new Headers();
    headers.append('Content-Type', 'application/json');
    return this.http.post('http://localhost:8000/',{ headers: headers ...})
        .map(res =>new Leaf(res.json()));//maybe I could do something here?
}

and here is my Leaf class just in case:

Leaf.ts

export class Leaf{
    name: string;
    state: string;
    treeData: Array<Leaf>;


    constructor(input:any){
        this.name = input.name;
        this.state = input.state;
        this.treeData = input.children;
    }

    toggleState() {
        if (this.state=='active'){
            this.state = 'inactive';
        }
        else {
            this.state = 'active'
        }
    }
}

My final goal is to get the json tree and represent them in a folder tree format. Is there a way to use map() to go through all nodes or combination of map() and some sort of traverser?

Answer 1

I'd first create an interface for the json data:

interface LeafJson {
    name: string;
    state: string;
    children?: LeafJson[];
}

And then use Array.map to create the children:

export class Leaf {
    name: string;
    state: string;
    treeData: Array<Leaf>;

    constructor(input: LeafJson){
        this.name = input.name;
        this.state = input.state;
        this.treeData = input.children ? input.children.map(item => new Leaf(item)) : [];
    }

    toggleState() {
        if (this.state=='active'){
            this.state = 'inactive';
        } else {
            this.state = 'active'
        }
    }
}

( code in playground )