Virtual Attributes in objection.js

I need generate an extra field for every ticket I have. This new field will be a boolean indicating true if the number is 1 and false in any other value.
I can easily add a new field and generate the value according the rule I want but it’s kind silly to have an extra field in the table just for this flag.

Virtual Attributes

Objection.js allows me to generate any extra field according the values of a Model. This means I can generate a new field called isFirst and it will be generated dinamically by objection.

First I need to use the virtualAttributes method, it must return an array with the names of the fields I want to add to my results.

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static get virtualAttributes() {
  return ['isFirst'];
}

Now I need to define the isFirst as a function

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get isFirst() {
  return this.number === 1;
}

I am writing a new function and inside of it putting a simple condition, if the number is equal to 1 it should return true otherwise false.
The this keyword gives me access to the value of each row my query might contains.
It means that if I make a query like this:

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select id, number from ft_tickets where id = 1;

This will return one row

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{
	"id": 1,
	"number": 1
}

In this case the this.number will have the value of 1 and objection will add a new field called isFirst with the vaue of true.
The same logic applys if the query include many rows.

Output

If I executed node queries.js

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Ticket.query()
	.eager('type')
	.select('id', 'number')
	.then(tickets => {
		console.log('Is First?', tickets[0].isFirst);
		console.log('Is First?', tickets[1].isFirst);
	});

it will return the output:

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Ticket Types [ TicketType { id: 1, name: 'Customer', code: 'CUS' },
  TicketType { id: 2, name: 'VIP', code: 'VIP' },
  TicketType { id: 3, name: 'Regular', code: 'REG' } ]
Is First? true
Is First? false

Awesome like always 🇵🇪