Reconsider type annotations because of generic methods and compilation times about ios-handbook

[3lvis]

We should check for slowly compiled methods before doing something about them.
http://khanlou.com/2016/12/guarding-against-long-compiles

[3lvis]

Basically, you mean:

let percentage: Double = 10

Instead of:

let percentage = Double(10)

[elland]

👍

also not:

let percetange = 10 as Double

[3lvis]

We don't do that one, though.

[elland]

Not for this specific case. 🤔

Thinking about stuff like let json = json as? [String: Any] and there I think we should keep the as stuff for sure. No better way.

[elland]

So yeah, nevermind the as Double.

[3lvis]

What about:

let collectionView = UICollectionView()

Should it be:

let collectionView: UICollectionView = UICollectionView()

Or are you thinking in doing this for some specific cases?

[elland]

Only where type can't be correctly inferred. Code should be as verbose as needed but not verboser*

* not a real word

[3lvis]

Only where type can't be correctly inferred.

let percentage = Double(10)

What's incorrect about this?

[elland]

Nothing, it's just become inconsistent with the rest as we adopt type annotation instead. 👍

[3lvis]

So we have two options:

Option A:

Use type annotation when it's needed.

let percentage = Double(10)
let collectionView = UICollectionView()
lazy var view: UIView = {

}()

// Type annotation required here, it's obvious, if you don't add it won't work.
let generic: Generic = Generic(value: 1) * Generic(value: 2)

Option B:

Always use type annotation unless the type is obvious such as when assigning a new instance to a variable.

let percentage: Double = 10

// Type annotation is not needed here, since it's obvious looking at the result of UICollectionView()
let collectionView = UICollectionView() // Otherwise it would be let collectionView: UICollectionView = UICollectionView() 
lazy var view: UIView = {

}()
let generic: Generic = Generic(value: 1) * Generic(value: 2)

They both are pretty much the same, so I guess it all comes down to.

let percentage = Double(10)
let collectionView = UICollectionView()

vs

let percentage: Double = 10
let collectionView = UICollectionView()

[3lvis]

I think having the first one. "Use type annotation when it's needed." Makes more sense since it's easier to be more consistent, basically the only place where the rule will be violated will be when using generics, which is not that often.

Meanwhile. going for "Always use type annotation unless the type is obvious such as when assigning a new instance to a variable." means that you're violating the rule every time you do:

let collectionView = UICollectionView()

Which is several times in any app.

[elland]

I don't think I understood your point. The rule change would mean that instead of

let percentage = Double(10)

You'd do

let percentage: Double = 10

So it's consistent with generics, etc. 🤔What am I missing? I don't think anything else changes.

[3lvis]

The rule change it's only consistent with generics, which we don't use that often, not with:

let collectionView = UICollectionView()

Which is all over the place.

[elland]

But this doesn't change. It's still the same. 🤔

[designatednerd]

@elland I think this has improved sufficiently in Swift 4 that we don't need this as an official standard. Do you mind if I close this out?

[elland]

@designatednerd do we have numbers on that? 👍

[designatednerd]

Not officially, but we've got the toshi project set up to warn us if anything takes more than 200ms to compile. Even on my cranky old computer the number of things we've needed to add annotations to in order to help the compiler get its shit together was far outpaced by the number of things which just needed to be simplified.

[elland]

worth a try 👍