[swift-evolution] Proposal: Re-instate mandatory self for accessing instance properties and functions

[Dennis Lysenko]

> - only expose the minimum necessary amount of names in any scope

> - break functions into small part so that it's easy to see all the local
name declarations

> - not use any globals, or at least name them in a visually different way
(UppercaseCamelStyle)

> - name properties and locals in a different way (classProperty, local_var)

Ilya, I think this may be a presumptuous way of how well programmers code.
When deadlines hit, those first two suggestions go out the window. And the
fourth/last suggestion is not valid for me - changing naming conventions
would be both more confusing and more work (context switching) than
explicit self.


The other tangible benefit of explicit self is that code becomes more
refactorable. You can move code to and from closures at will, and moving it
to unsuitable contexts gives immediate negative feedback. This is actually
the reason why my team chose unanimously to adopt explicit self as a strict
code style guideline.


-1 to the notion that it makes the transition from global state to class
state less fluid. Global state and class state should never be conflated
and implicit self can lead to such conflation. Global functions should be
carefully rewritten to class dynamics when the transition is desired, and
implicit self makes it easier to make that transition without careful
consideration.


Overall, I give +1 to the explicit self proposal, -1 to using a special
operator. Explicit self is neither hard nor particularly verbose in my
experience; with syntax highlighting, it happens to be very readable. I
love Ruby, but an @ operator for ivars would be very foreign and would kill
the aesthetic of the language for me. Not sure where others stand on it.

On Sun, Dec 13, 2015, 4:16 AM ilya via swift-evolution <
swift-evolution at swift.org> wrote:

> > But implicit self is confusing in a lot of code
>
> On the other hand, it allows a logical explanation of how you can take
> code from global scope and put it into an instance scope:
>
> let greeting = "Hello"
> let name = "Michael"
>
> func greet() {
>     print("\(greeting), \(name)")
> }
>
> seemlessly becomes
>
> class Greeter {
>
>     let greeting = "Hello"
>     let name = "Michael"
>
>     func greet() {
>         print("\(greeting), \(name)")
>     }
>
> }
>
> > can (and does) lead to shadowing bugs,
>
> There are simple strategies that help to minimize the amount of shadowing,
> e.g.
>
> - only expose the minimum necessary amount of names in any scope
> - break functions into small part so that it's easy to see all the local
> name declarations
> - not use any globals, or at least name them in a visually different way
> (UppercaseCamelStyle)
> - name properties and locals in a different way (classProperty, local_var)
>
> Even without a formal code style, if you tend to make property names
> longer and local names shorter, your risk of shadowing goes down.
>
> > .x and .f() to mark implicit self. I realize that this may conflict with
> enum usage.
>
> This will lead to a lot of ambiguity:
>
> func f() {
>     let x = NSOperation()
>     .name = "Name" // is it x.name or self.name??
>    ...
> }
>
> >  If so, then use another marker. For instance :x or ^x or anything.
>
> This is workable, but still I think this is one of the best points of
> Swift – the existence of instance scope where names are simply written
> as-is. This helps implementing patterns like "take a long function and make
> it into a struct with a bunch of small functions instead".
>
> > is very difficult to reason about in diffs or any other interface that
> isn't an IDE (especially code review)
>
> This is the point where I entirely agree, good code should be easily read
> in any context.
> Again, may I suggest you take a look into using a style guide to
> differentiate visually between local and instance scope?
>
> Ilya
>
> On Sun, Dec 13, 2015 at 10:15 AM, Rob Napier via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> I wanted to reopen this discussion that seems to have trailed off.
>> Requesting the return of self was my very first ask of Swift if I remember
>> correctly (https://devforums.apple.com/message/1013085). Continued work
>> in Swift has both strengthened and modified that ask. Here are several of
>> the examples discussed before:
>>
>> https://gist.github.com/schwa/94b11dc0a7a331f46b25
>> https://gist.github.com/rnapier/478465d1b15e95b98b42
>> https://gist.github.com/rnapier/4213dc64206b17df6935
>> https://gist.github.com/dwineman/d6c56ec0c0e2fdb761db
>>
>> I get that it seems tedious to type (and read) "self." and I get that
>> "self." is currently a hint that self might be captured (but doesn't
>> actually mean that, since you can use self. without capturing, and
>> sometimes have to, very often in init, so really it's basically meaningless
>> for that use).
>>
>> That's why I suggest using .x and .f() to mark implicit self. I realize
>> that this may conflict with enum usage. If so, then use another marker. For
>> instance :x or ^x or anything. But implicit self is confusing in a lot of
>> code, can (and does) lead to shadowing bugs, and is very difficult to
>> reason about in diffs or any other interface that isn't an IDE (especially
>> code review).
>>
>> Thoughts, David? I agree with your basic proposal; I just want to amend
>> it.
>>
>> -Rob
>>
>>
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>>
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