[swift-evolution] [swift-evolution-announce] [Review] SE-0023 API Design Guidelines

[Thorsten Seitz]

> Am 23.01.2016 um 01:35 schrieb Erica Sadun via swift-evolution <swift-evolution at swift.org>:
> 
>> 
>> On Jan 22, 2016, at 5:26 PM, Michael Wells via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> 
>>> On Sat, Jan 23, 2016 at 12:00 AM, David Owens II via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>> Compensate For Weak Type Information as needed to clarify a parameter’s role.
>>>> 
>>>> Especially when a parameter type is NSObject, Any, AnyObject, or a fundamental type such Int or String, type information and context at the point of use may not fully convey intent. In this example, the declaration may be clear, but the use site is vague:
>>>> 
>>>> func add(observer: NSObject, for keyPath: String)
>>>> grid.add(self, for: graphics) // vague
>>>> 
>>>> To restore clarity, precede each weakly-typed parameter with a noun describing its role:
>>>> 
>>>> func addObserver(_ observer: NSObject, forKeyPath path: String)
>>>> grid.addObserver(self, forKeyPath: graphics) // clear
>>> 
>> 
>> Where this rule feels clumsy to me is in code such as
>> 
>> func loginWithUsername(username: String, password: String) -> Bool
>> 
>> vs.
>> 
>> func login(username: String, password: String) -> Bool
>> 
>> But maybe it just takes some time to get used to the style.
> 
> 
> Consider an exception rule:
> 
> Prefer external names for the first parameter when the natural semantic relationship between the parameters is stronger than their relation to the operation. So
> 
> login(username: String, password:String)

I would actually prefer one of

func loginWithUsername(username: String, password: String)
func login(withUsername username: String, password: String)

because of the weak type information to just

func login(sername: String, password: String)


Of course the ideal version would define the types Username and Password (ideally with a future newtype construct :-) and then could use just

func login(username: Username, password: Password)


> but 
> 
> addLineToPoint(p1: CGPoint, withThickness: CGFloat)

Why should addLineTo(point: CGPoint, withThickness thickness: CGFloat) be considered as having weak type information for the point?


-Thorsten

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