On 22.07.2016 19:25, Duan wrote:
The current syntax establishes a relationship.
X: Y
means "X will have interface of Y". Note there's no mention of inheritance or
protocol here: they both establish this relationship. This is why we can use
z is Y
To check whether such relationship holds. Again, there's no need to worry
whether Y is a class or protocol.
But we see that some mature languages like Java, C# and C++, Object Pascal
has this distinction: Java with 'implements' keyword, C# with 'I' prefix
for interfaces(their protocols), C++ with both `implements` and 'I' prefix
conversion, Object Pascal with 'I' prefix. I.e. I believe that in any case
new syntax will establish a relationship, but more clearly distinct
inheritance with conformance to help the reader to understand the
composition of the reviewed class code.
That being said, I agree that user have to look up Y's declaration to determine which one
they are writing/reading. But is that a real issue? Why would you write/use "class
X: Y {}" before knowing what Y is?
The problem arises not when you write/use but when you *read* someone's
code, and sometimes you read that code not in XCode/IDE.
Daniel Duan
Sent from my iPhone
On Jul 22, 2016, at 6:14 AM, Vladimir.S via swift-evolution
<[email protected]> wrote:
I remember that this was discussed, but can't find any decision regarding
this.. So, as a last chance, don't we want in Swift 3.0, as big source breaking
change, separate class inheritance and protocol conformance in syntax?
Sorry if there was a decision about this suggestions. Please let know in this
case.
I.e. when I see the following I can't understand if the class inherits from
base class and conforms to protocols or just conforms to two protocols:
class MyClass : First, Second, Third {
}
We don't have a rule to name protocols with 'Protocol'/other suffix/prefix, or
classes with 'T'/'C' prefix or something like this, so I believe to improve the
clarity of code we should separate in syntax inheritance and conformance.
As I understand we should discuss changes in these areas:
1. class inheritance :
class Child: BaseClass
2. class conformance :
class Child: SomeProtocol1, SomeProtocol2
3. class inheritance + conformance :
class Child: BaseClass, SomeProtocol1, SomeProtocol2
4. protocol conformance for structs:
struct Struct: SomeProtocol1, SomeProtocol2
5. protocol inheritance:
protocol Child: BaseProtocol1, BaseProtocol2
My suggestions:
I) separate inheritance with double colon :
1. class inheritance :
class Child:: BaseClass
2. class conformance :
class Child: SomeProtocol1, SomeProtocol2
3. class inheritance + conformance :
class Child:: BaseClass : SomeProtocol1, SomeProtocol2
4. protocol conformance for structs:
struct Struct: SomeProtocol1, SomeProtocol2
5. protocol inheritance:
protocol Child:: BaseProtocol1, BaseProtocol2
II) in class definition use parenthesis to separate inheritance and conformance
:
1. class inheritance :
class Child: BaseClass
2. class conformance :
class Child: (SomeProtocol1, SomeProtocol2)
3. class inheritance + conformance :
class Child: BaseClass (SomeProtocol1, SomeProtocol2)
4. protocol conformance for structs:
struct Struct: SomeProtocol1, SomeProtocol2
or
struct Struct: (SomeProtocol1, SomeProtocol2)
should be discussed
5. protocol inheritance:
protocol Child: BaseProtocol1, BaseProtocol2
III) special word like 'conforms'
1. class inheritance :
class Child: BaseClass
2. class conformance :
class Child: conforms SomeProtocol1, SomeProtocol2
or
class Child conforms SomeProtocol1, SomeProtocol2
3. class inheritance + conformance :
class Child: BaseClass conforms SomeProtocol1, SomeProtocol2
4. protocol conformance for structs:
struct Struct: conforms SomeProtocol1, SomeProtocol2
or
struct Struct conforms SomeProtocol1, SomeProtocol2
5. protocol inheritance:
protocol Child: BaseProtocol1, BaseProtocol2
Thoughts?
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