[swift-evolution] What about renaming Optional.map to Optional.mapMe ?

Derrick Ho wh1pch81n at gmail.com
Tue Dec 6 20:58:00 CST 2016

Jay, I fail to see the point you are trying to make. Can you clarify why we
need a new map method for an optional array of elements?

On Tue, Dec 6, 2016 at 9:46 PM Jay Zhao via swift-evolution <
swift-evolution at swift.org> wrote:

It applies in theory to think Optional as a collect of one and for that
reason map is a perfect name.

But in practice, we often use the same variable name for *array* and
*array?* .  So when you see :
You can not tell which map and even worse which $0 it is.

According to Swift API Design Guidelines *#1*, *Clarity at the point of use*
And to combine theory and practice, I propose *mapUnwrapped* to remove the

Actually this is what’s been adopted in my company:

public extension Optional {

    /// Pass the `Optional` into the closure that returns `Non-Optional`

    public func mapUnwrapped<U>(_ transform: (Wrapped) throws -> U) rethrows
-> U? {

        return try map(transform)



To summary my idea:
This is the situation where usability > design purity for a language(a

On 7 Dec 2016, at 08:05, Robert Widmann <devteam.codafi at gmail.com> wrote:

If you think of Optional as a zero-or-one element collection there's really
no reason this operation should be named any differently.  It still lifts a
function over values to one over Optionals.  It still extracts the contents
of the structure and applies the function (propagating failure if
necessary).  The operation is no different from the one required of a plain
Sequence conformance, why should it have a new name if it is not a new

~Robert Widmann

2016/12/05 22:46、Jay Zhao via swift-evolution <swift-evolution at swift.org>

Hi there,

Code explains everything:

/// Maybe a bad API naming in Swift? See below:

        /// array1 can be array of any object that have a `count` method
        let array1 = [[String]]()
        let array2 :[String]? = nil

        // I believe the confusion between `array.map` and
`optionalArray.map` is really bad.
        // Because when you read code like this, you can not tell which is
        _ = array1.map({$0.count})
        _ = array2.map({$0.count})

        // It can be clearer:
        // 1, we pass `self.element` into the closure
        _ = array1.map({$0.count})
        // 2, we pass self directly into the closure
        _ = array2.mapMe({$0.count})

The mapFlat method is also problematic.

Jay Zhao

swift-evolution mailing list
swift-evolution at swift.org

swift-evolution mailing list
swift-evolution at swift.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20161207/22154092/attachment.html>

More information about the swift-evolution mailing list