support factory-function in .default() ?

[Bartvds]

As the readme notes using an reference-type as the value for default makes the same instance shared by all invocations, which is not that useful.

Would it be an idea to allow a function as value, to be called when a new default value is needed so it can produces a new instance?

[hueniverse]

Nah. If you need unique instances of a default object you should move that logic to code after validation.

[Starefossen]

This would be useful for things like:

var schema = Joi.object().keys({
  created: Joi.date().default(Date.now)
});

[jedireza]

👍 I had the same use case @Starefossen shared.

[pward123]

+1 same use case as @Starefossen

[silas]

+1

[satazor]

+1

[Marsup]

Is the only use case to accept 'now' as is already the case in min and max ?

[silas]

No, I certainly have other use cases, such as special cases of Date.now (such as 00:00 of today), uuids, expire times (30 minutes from now), etc..

Obviously it's easy to do this in code, but it would be nice to be able to just pass default a function.

[satazor]

@Marsup I got an use case for now but I've a more complex case where I need to infer a default value based on the contents of another property:

{
   artists: [{ name: 'Madonna', role: 'main' }]
   display_artist: 'Madonna'
}

The display_artist is a "required" field that defaults to a string built manually from the artists array. If I could pass a function in default() it would look like this:

{
   artists: Joi.array()....,
   display_artist: Joi.string().trim().default(function (obj) {
     return obj.artists.reduce(function (previousVal, currentVal) {
         return previousVal += currentVal.name + ' ';
     }, '').trim();
   })
}

At the moment I'm doing the complex "default" stuff like this after Joi validation.

[bleupen]

+1

[briansorahan]

+1 I could benefit from two of the use cases mentioned already: Date.now and uuid.

[rtyer]

+1 Same here on date and uuid generation.

[pekeler]

+1

[wspringer]

+1

[pekeler]

Nice :)

[bleupen]

so is this a breaking change for existing joi.func().default(fn) schema expressions?

[Marsup]

Thanks @bleupen, this one slipped through the reviews, we'll fix that before release.

[Marsup]

Fixed by #555.

[bleupen]

I'm very hapi you guys are working on this one, although something feels wrong about the modal nature of default() based on the presence of a description attribute. It violates the principal of least surprise imo. Have you considered adding a factory() instead and preserve the existing behavior of default()?

Sent from my iPhone

On Feb 18, 2015, at 3:31 PM, Nicolas Morel notifications@github.com wrote:

Fixed by #555.

—
Reply to this email directly or view it on GitHub.

[Marsup]

I don't understand, this is not a breaking change, default will continue to work as it is today, it's just an improvement.

[bleupen]

It’s really only an issue when the item type is joi.func() (i use this feature a lot to sanitize drivers). In this case, if I understand correctly, adding a second description parameter to default() is what throws joi into "higher order function mode”. While non-breaking, it feels surprising to me. Perhaps I’m misreading the code.

On Feb 18, 2015, at 3:31 PM, Nicolas Morel notifications@github.com wrote:

Fixed by #555 #555.

—
Reply to this email directly or view it on GitHub #363 (comment).

[Marsup]

That or having a description property on your function. Why is that surprising ?

[bleupen]

Because whether a function is a factory or not is orthogonal to its description. Not a huge deal, I can definitely work with whats here.

On Feb 18, 2015, at 4:37 PM, Nicolas Morel notifications@github.com wrote:

That or having a description property on your function. Why is that surprising ?

—
Reply to this email directly or view it on GitHub #363 (comment).

[Marsup]

I think it's clearer this way, I don't want a debate about whether default or factory wins if both exists :)

Joke aside, the description is more of a side-effect that's needed if we want to keep the ability to describe validations. I see it the other way around, the description is needed because you provided a function, it doesn't make the function special, except in the Joi.func() case you highlighted.

[lock]

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