[swift-users] [swift-evolution] for-else syntax

[Erica Sadun]

I've taken this over to Swift Users from Swift Evolution.

I think you'd want to handle the exceptional case first, as it provides an opportunity for early exit before processing normal behavior. In such case, consider using a guard rather than an if:

guard !names.isEmpty else { print("No names"; return }
for name in names { ... }

Flipping the two tests allows you to use an existing if-else without changing the language, although there's really nothing that the `else` is adding here:

if names.isEmpty { ... }
else for name in names { ... }

-- E



> On Feb 1, 2017, at 10:31 AM, Saagar Jha via swift-evolution <swift-evolution at swift.org> wrote:
> 
> If you’re fine with a couple extra characters, you can use .isEmpty:
> 
> for name in names {
> 	// do your thing
> }
> if names.isEmpty {
> 	// do whatever
> }
> 
> It’s a bit more typing, but I feel it makes your intentions more clear.
> 
> Saagar Jha
> 
>> On Feb 1, 2017, at 8:48 AM, Chris Davis via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Hi,
>> 
>> Often when I’m programming I stumble upon this scenario:
>> 
>> I have a list of items that may or may not be empty - if it’s full, I do one thing, if it’s empty I do something else, my code looks like this:
>> 
>> class Example_1
>> {
>>     let names = ["Chris", "John", "Jordan"]
>>     
>>     /// Loop over names, if no names, print no names
>>     func run()
>>     {
>>         for name in names
>>         {
>>             print(name)
>>         }
>>         
>>         if names.count == 0
>>         {
>>             print("no names")
>>         }
>>     }
>> }
>> 
>> let exampleOne = Example_1()
>> exampleOne.run()
>> 
>> However, Personally, I would find it more pleasing to write something like this:
>> 
>> class Example_2_Proposed
>> {
>>     let names:[String] = []
>>     
>>     /// Loop over names, if no names, print no names
>>     func run()
>>     {
>>         for name in names
>>         {
>>             print(name)
>>         } else {
>>             print("no names")
>>         }
>>     }
>> }
>> 
>> let exampleTwo = Example_2_Proposed()
>> exampleTwo.run()
>> 
>> The difference here is a “for-else” type syntax where if there were no items in the array it would simply fall through to the else statement.
>> 
>> What would be the pros/cons of introducing such syntax?
>> 
>> Is there’s a way of doing something similar in swift already?
>> 
>> Thanks
>> 
>> Chris
>> 
>> 
>> 
>> 
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>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
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> 
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