Setters for object arrays in ES6

Question

I have a class that contains an array that is used to contain objects of a certain type.

class Test {
    constructor() {
      this.objects = [];
    }

    # Only objects with positive foobars should be returned
    get objects() { return this.objects.filter(o => o.foobar >= 0); }
}

I don't need any special treatment for setting values in the array, so I didn't write a set method. But now I get an error saying I cannot write to a property that only has a getter method. So I tried to reconstruct the default setter method like so:

set objects(k,v) { this.objects[k] = v; }
set objects[k](v) { this.objects[k] = v; }
set objects(v) { this.objects = v; }

But none of the above work. I simply want to be able to set values in the array as usual via this.objects[2] = foobar; How do I tell ES6 that?

oops, sorry, that was a typo in the post... The error still persists :-( — DP.
– DP., Commented Apr 6, 2017 at 14:41
Sorry for all the typos, my original code is way more complex so I wrote this example from scratch without testing it... — DP.
– DP., Commented Apr 6, 2017 at 14:45

To-xic · Accepted Answer · 2017-04-06 14:45:00Z

3

You can't write the objects in objects in getter. It may cause maximum call. I advice you to write in this way.

class Test {
  construct() {
    this.objects = [];
  }
  get legalobjects() { 
    return this.objects.filter(o => o.foobar >= 0);
  }
}

In which way you can set object as you want

answered Apr 6, 2017 at 14:45

To-xic

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trincot · Accepted Answer · 2017-04-06 14:43:28Z

2

You should name the object property and prototype's getter differently, otherwise the constructor will try to find the setter that corresponds to the prototype's (class's) getter when it does this.objects = ....

class Test {
    constructor() {
      this.objects = [];
    }

    get positiveObjects() { this.objects.filter(o => o.foobar >= 0); }
}

NB: Your constructor method is named wrongly. It should be constructor, not construct. In the mean time you corrected it.

answered Apr 6, 2017 at 14:43

trincot

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2 Comments

DP. Over a year ago

OK, thank you, I didn't think of using a different name for the getters and setters than the original property name. This is different in Ruby...

trincot Over a year ago

Note that the plain property you assign in the constructor is not a setter. A setter can be defined with the set keyword, much like get, but it would be used to completely replace the current array with a new one. There are many other ways to deal with this, for instance by extending Array.

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