[swift-evolution] "Assume" directive for classes and methods

[Jordan Rose]

> On Dec 23, 2015, at 9:14 , Joe Groff via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> 
>> On Dec 23, 2015, at 7:36 AM, D. Felipe Torres via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> I've been reading the discussion in "Final by default for classes and methods" and although I don't have a strong position towards what the default behaviour should be, I think a directive to change that behaviour should be added as when nullability was introduced into Obj-C.
>> 
>> In the current model of Swift, where methods and classes are not final we can ease that by doing something like this:
>> 
>> ASSUME_FINAL_BEGIN
>> class MyClass {
>>     func aMethod(arg: String) {
>>         
>>     }
>>     
>>     func anotherMethod(number: Int) {
>>         
>>     }
>> }
>> ASSUME_FINAL_END
>> 
>> 
>> In this example the whole class is treated as final by the compiler.
>> On the other hand, in the following example:
>> 
>> class MyClass {
>> ASSUME_FINAL_BEGIN
>>     func aMethod(arg: String) {
>>         
>>     }
>> ASSUME_FINAL_END    
>>     func anotherMethod(number: Int) {
>>         
>>     }
>> }
>> 
>> Only aMethod is final, leaving the rest to the default behaviour. (Ok, the example is not different to prepending 'final' but you get the idea).
>> 
>> Similarly, should the classes and methods become final by default, a directive to do the opposite should be added (ASSUME_OVERRIDEABLE_(BEGIN|END)?)
> 
> We tried to avoid these kinds of contextual blocks because they make reading declarations in isolation much harder. That's one of the reasons we have 'public'/'private' as per-decl modifiers rather than C++/ObjC-style grouping.

One of the primary reasons we have the "regions" in Objective-C is because we have existing large bodies of code that need to be audited and annotated. The intent there is to set up a reasonable default, and just mark that a particular section follows that default, rather than to have some code inside regions and some code outside.

Jordan

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151223/03a6a7a5/attachment.html>