Feature request: Exact Array

[esamattis]

First of all thanks for this awesome library!

This can be also a documentation issue because I could not figure out how to do it. I'd like to have a way to validate that I have some exact array in my object.

For example

{
  "ducks": [
    {"age": 1},
    {"age": 7}
  ]
}

Closest thing I managed to create is this:

var YoungDuck = schema({ age: 1 });
var OldDuck = schema({ age: 7 });

var Animals = schema({
  ducks: schema({
    0: YoungDuck,
    1: OldDuck
  }),
})

but this of course validates this too

{
  "ducks": [
    {"age": 1},
    {"age": 7},
    {"age": "bad!"}
  ]
}

Could it be possible to have something like this?

var Animals = schema({
  ducks: Array.exact([
    YoungDuck,
    OldDuck
  ]),
})

[molnarg]

There should be a simpler way to do it, but for now, try this:

var YoungDuck = schema({ age: 1 });
var OldDuck = schema({ age: 7 });

var Animals = schema({
  ducks: schema({
    0: YoungDuck,
    1: OldDuck,
    '*': null, // or length : 2
    constructor: Function.reference(Array)
  }),
})

The only modification I made to your example is that I added the '*': null, and the constructor: Function.reference(Array) attribute. If you don't need it to be a real array, just remove the constraint for the constructor.

Also consider using the deep equality pattern if applicable in your case ([[ { age: 1 }, { age: 7 } ]])

I think that the array handling of js-schema is still very immature, and it would be nice to solve its issues in a more general way. But for now, your Array.exact is the best quick solution I can think of. I will close this ticket for now, but feel free to send a pull request with an Array.exact implementation. Array handling will definitely be improved in the future.

[molnarg]

By the way, you don't need to nest schema calls inside schema calls, so the simplified solution would be this:

var YoungDuck = schema({ age: 1 });
var OldDuck = schema({ age: 7 });

var Animals = schema({
  ducks: {
    0: YoungDuck,
    1: OldDuck,
    '*': null, // or length : 2
    constructor: Function.reference(Array)
  }
})