Object instance is cast to Object after assignment

Question

I have class to which I set property values in a for loop. One of the properties is object, class respectively.

But after the for loop ends, this property loses its type and it is cast to simple Object. Why?

public setAttributes(data:any):void {
   for (var name in data) {
       if (this.hasOwnProperty(name)) {
            switch (name) {
                case 'restaurant':
                    this.restaurant = new Restaurant(data.restaurant);
                    console.log(this.restaurant); //log 1
                default:
                    this[name] = data[name];
            }
        }
    }
    console.log(this.restaurant); //log 2
    this.restaurant = new Restaurant(data['restaurant']);
    console.log(this.restaurant); //log 3
}

Calling function with

this.setAttributes({
    title: 'test',
    restaurant: {
        title: 'restaurant test'
    }
})

results in

Restaurant {title: 'restaurant test'} //log 1
Object {title: 'restaurant test'} //log 2
Restaurant {title: 'restaurant test'} //log 3

Why the second log (//log 2) has type Object but not Restaurant?

Thanks for your replies.

Ryan Cavanaugh · Accepted Answer · 2017-03-10 18:17:12Z

4

You need a break statement here to avoid overwriting this.restaurant right after you initialize it:

public setAttributes(data:any):void {
   for (var name in data) {
       if (this.hasOwnProperty(name)) {
            switch (name) {
                case 'restaurant':
                    this.restaurant = new Restaurant(data.restaurant);
                    console.log(this.restaurant); //log 1
                    break; // oops! was falling through
                default:
                    this[name] = data[name];
            }
        }
    }
    console.log(this.restaurant); //log 2
    this.restaurant = new Restaurant(data['restaurant']);
    console.log(this.restaurant); //log 3
}

answered Mar 10, 2017 at 18:17

Ryan Cavanaugh

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1 Comment

miro Over a year ago

thank you :) I was wondering about some JS behaviour I do not know. And look at that, what a silly mistake

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