Re: [swift-users] object.self?
Yes, as far as I know 'foo' and 'foo.self' are equivalent. I don't actually
know why the latter exists, except in analogy to "T.self".
There was a mistake in my response; the metatype of 'foo' is not
'foo.self', it is 'foo.dynamicType' (or whatever new form dynamicType is
going to take in Swift 3).
On Sat, Jul 9, 2016 at 2:27 PM, Rick Mann wrote:
>
> > On Jul 8, 2016, at 09:45 , Austin Zheng wrote:
> >
> > Hi Rick,
> >
> > If you have a type (let's call it "T"), you can use it two ways:
> >
> > * As a type, or part of a type, like such: "let x : T = blah()"
> > * As a value, just like any other variable, function argument, property,
> etc.
> >
> > In the second case (type-as-value), you need to append ".self" to the
> type name according to the grammar:
> >
> > "let x : Any.Type = T.self"
> >
> > There was a "bug" in Swift 2.x where you could sometimes use just "T",
> without the ".self", in certain cases (in particular, when you were passing
> in a type-as-value to a function with one unlabeled argument). That bug has
> since been fixed.
> >
> > As for types-as-values: Swift allows you to treat a type as a normal
> value, which means you can do whatever you want with it: pass it to
> functions and return it from functions, store it in properties or
> variables, etc. If you have one of these types-as-values (called
> 'metatypes'), you can do certain things like call static methods or
> initializers on them, use them to parameterize generic functions, etc.
>
> Thanks, Austin. I'm familiar with all this in Swift. What threw me was
> that "subclassObject" was an instance, not a class.
>
> > However, to get back to your original question, the `.self` in that
> switch statement actually isn't necessary and you should really just be
> switching on the value of subclassObject itself, not the value of its type.
>
> I would have thought so, but the response to this answer was something
> along the lines of "I never know when to use the object or its self."
>
> To me, for an instance, foo an foo.self should be equivalent in all
> respects (shouldn't it?).
>
> >
> > Best,
> > Austin
> >
> >
> > On Fri, Jul 8, 2016 at 9:38 AM, Rick Mann via swift-users <
> swift-users@swift.org> wrote:
> > I just saw a question which brought up something I didn't know about.
> Apparently sometimes you have to call object.self in a place that looks
> like you should just use "object." What does this usage mean?
> >
> > for subclassObject in objects {
> > switch subclassObject.self {<--- Here, why not
> "subclassObject" alone?
> > case is Subclass1:
> > doSomethingWith(subclassObject as! Subclass1)
> >
> > case is Subclass2:
> > doSomethingWith(subclassObject as! Subclass2)
> >
> > case is Subclass3:
> > doSomethingWith(subclassObject as! Subclass3)
> >
> > default:
> > break
> > }
> > }
> >
> > Thanks,
> > Rick
> >
> > > On Jul 8, 2016, at 08:15 , Dan Loewenherz via swift-users <
> swift-users@swift.org> wrote:
> > >
> > > To my knowledge, you can’t do exactly what you’re trying to do, but
> this is close:
> > >
> > > for subclassObject in objects {
> > > switch subclassObject.self {
> > > case is Subclass1:
> > > doSomethingWith(subclassObject as! Subclass1)
> > >
> > > case is Subclass2:
> > > doSomethingWith(subclassObject as! Subclass2)
> > >
> > > case is Subclass3:
> > > doSomethingWith(subclassObject as! Subclass3)
> > >
> > > default:
> > > break
> > > }
> > > }
> > >
> > > On Fri, Jul 8, 2016 at 10:11 AM, Nate Birkholz via swift-users <
> swift-users@swift.org> wrote:
> > > This looks like it doesn't work (swift 2.x), but wanted to be sure
> it's not supported:
> > > class Superclass {}
> > > class Subclass1 : Superclass {}
> > > class Subclass2 : Superclass {}
> > > class Subclass3 : Superclass {}
> > >
> > > let sc1 = Subclass1()
> > > let sc2 = Subclass2()
> > > let sc3 = Subclass3()
> > >
> > > let objects : [Superclass] = [sc1, sc2, sc3]
> > >
> > > for subclassObject in objects {
> > > switch subclassObject {
> > > case let object = subclassObject as? Subclass1:
> > > doSomethingWith(object)
> > > case let object = subclassObject as? Subclass2:
> > > doSomethingWith(object)
> > > case let object = subclassObject as? Subclass3:
> > > doSomethingWith(object)
> > > default:
> > > return
> > > }
> > > }
> > >
> > > This gives an error, expecting a colon (:) after object on every case.
> > >
> > > I wanted to be sure I wasn't missing something in my syntax (nor some
> obvious-to-others reason this isn't supported) before going to swift
> evolution.
> > >
> > >
> > > --
> > > Nate Birkholz
> > >
> > > ___
> > > swift-users mailing list
> > > swift-users@swift.org
> > > https://lists.swift.org/mailman/listinfo/swift-users
> > >
> > >
> > > ___
> > > swift-users ma
Re: [swift-users] object.self?
> On Jul 8, 2016, at 09:45 , Austin Zheng wrote:
>
> Hi Rick,
>
> If you have a type (let's call it "T"), you can use it two ways:
>
> * As a type, or part of a type, like such: "let x : T = blah()"
> * As a value, just like any other variable, function argument, property, etc.
>
> In the second case (type-as-value), you need to append ".self" to the type
> name according to the grammar:
>
> "let x : Any.Type = T.self"
>
> There was a "bug" in Swift 2.x where you could sometimes use just "T",
> without the ".self", in certain cases (in particular, when you were passing
> in a type-as-value to a function with one unlabeled argument). That bug has
> since been fixed.
>
> As for types-as-values: Swift allows you to treat a type as a normal value,
> which means you can do whatever you want with it: pass it to functions and
> return it from functions, store it in properties or variables, etc. If you
> have one of these types-as-values (called 'metatypes'), you can do certain
> things like call static methods or initializers on them, use them to
> parameterize generic functions, etc.
Thanks, Austin. I'm familiar with all this in Swift. What threw me was that
"subclassObject" was an instance, not a class.
> However, to get back to your original question, the `.self` in that switch
> statement actually isn't necessary and you should really just be switching on
> the value of subclassObject itself, not the value of its type.
I would have thought so, but the response to this answer was something along
the lines of "I never know when to use the object or its self."
To me, for an instance, foo an foo.self should be equivalent in all respects
(shouldn't it?).
>
> Best,
> Austin
>
>
> On Fri, Jul 8, 2016 at 9:38 AM, Rick Mann via swift-users
> wrote:
> I just saw a question which brought up something I didn't know about.
> Apparently sometimes you have to call object.self in a place that looks like
> you should just use "object." What does this usage mean?
>
> for subclassObject in objects {
> switch subclassObject.self {<--- Here, why not "subclassObject"
> alone?
> case is Subclass1:
> doSomethingWith(subclassObject as! Subclass1)
>
> case is Subclass2:
> doSomethingWith(subclassObject as! Subclass2)
>
> case is Subclass3:
> doSomethingWith(subclassObject as! Subclass3)
>
> default:
> break
> }
> }
>
> Thanks,
> Rick
>
> > On Jul 8, 2016, at 08:15 , Dan Loewenherz via swift-users
> > wrote:
> >
> > To my knowledge, you can’t do exactly what you’re trying to do, but this is
> > close:
> >
> > for subclassObject in objects {
> > switch subclassObject.self {
> > case is Subclass1:
> > doSomethingWith(subclassObject as! Subclass1)
> >
> > case is Subclass2:
> > doSomethingWith(subclassObject as! Subclass2)
> >
> > case is Subclass3:
> > doSomethingWith(subclassObject as! Subclass3)
> >
> > default:
> > break
> > }
> > }
> >
> > On Fri, Jul 8, 2016 at 10:11 AM, Nate Birkholz via swift-users
> > wrote:
> > This looks like it doesn't work (swift 2.x), but wanted to be sure it's not
> > supported:
> > class Superclass {}
> > class Subclass1 : Superclass {}
> > class Subclass2 : Superclass {}
> > class Subclass3 : Superclass {}
> >
> > let sc1 = Subclass1()
> > let sc2 = Subclass2()
> > let sc3 = Subclass3()
> >
> > let objects : [Superclass] = [sc1, sc2, sc3]
> >
> > for subclassObject in objects {
> > switch subclassObject {
> > case let object = subclassObject as? Subclass1:
> > doSomethingWith(object)
> > case let object = subclassObject as? Subclass2:
> > doSomethingWith(object)
> > case let object = subclassObject as? Subclass3:
> > doSomethingWith(object)
> > default:
> > return
> > }
> > }
> >
> > This gives an error, expecting a colon (:) after object on every case.
> >
> > I wanted to be sure I wasn't missing something in my syntax (nor some
> > obvious-to-others reason this isn't supported) before going to swift
> > evolution.
> >
> >
> > --
> > Nate Birkholz
> >
> > ___
> > swift-users mailing list
> > swift-users@swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
> >
> >
> > ___
> > swift-users mailing list
> > swift-users@swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
>
>
> --
> Rick Mann
> rm...@latencyzero.com
>
>
> ___
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
--
Rick Mann
rm...@latencyzero.com
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] object.self?
Hi Rick,
If you have a type (let's call it "T"), you can use it two ways:
* As a type, or part of a type, like such: "let x : T = blah()"
* As a value, just like any other variable, function argument, property,
etc.
In the second case (type-as-value), you need to append ".self" to the type
name according to the grammar:
"let x : Any.Type = T.self"
There was a "bug" in Swift 2.x where you could sometimes use just "T",
without the ".self", in certain cases (in particular, when you were passing
in a type-as-value to a function with one unlabeled argument). That bug has
since been fixed.
As for types-as-values: Swift allows you to treat a type as a normal value,
which means you can do whatever you want with it: pass it to functions and
return it from functions, store it in properties or variables, etc. If you
have one of these types-as-values (called 'metatypes'), you can do certain
things like call static methods or initializers on them, use them to
parameterize generic functions, etc.
However, to get back to your original question, the `.self` in that switch
statement actually isn't necessary and you should really just be switching
on the value of subclassObject itself, not the value of its type.
Best,
Austin
On Fri, Jul 8, 2016 at 9:38 AM, Rick Mann via swift-users <
swift-users@swift.org> wrote:
> I just saw a question which brought up something I didn't know about.
> Apparently sometimes you have to call object.self in a place that looks
> like you should just use "object." What does this usage mean?
>
> for subclassObject in objects {
> switch subclassObject.self {<--- Here, why not
> "subclassObject" alone?
> case is Subclass1:
> doSomethingWith(subclassObject as! Subclass1)
>
> case is Subclass2:
> doSomethingWith(subclassObject as! Subclass2)
>
> case is Subclass3:
> doSomethingWith(subclassObject as! Subclass3)
>
> default:
> break
> }
> }
>
> Thanks,
> Rick
>
> > On Jul 8, 2016, at 08:15 , Dan Loewenherz via swift-users <
> swift-users@swift.org> wrote:
> >
> > To my knowledge, you can’t do exactly what you’re trying to do, but this
> is close:
> >
> > for subclassObject in objects {
> > switch subclassObject.self {
> > case is Subclass1:
> > doSomethingWith(subclassObject as! Subclass1)
> >
> > case is Subclass2:
> > doSomethingWith(subclassObject as! Subclass2)
> >
> > case is Subclass3:
> > doSomethingWith(subclassObject as! Subclass3)
> >
> > default:
> > break
> > }
> > }
> >
> > On Fri, Jul 8, 2016 at 10:11 AM, Nate Birkholz via swift-users <
> swift-users@swift.org> wrote:
> > This looks like it doesn't work (swift 2.x), but wanted to be sure it's
> not supported:
> > class Superclass {}
> > class Subclass1 : Superclass {}
> > class Subclass2 : Superclass {}
> > class Subclass3 : Superclass {}
> >
> > let sc1 = Subclass1()
> > let sc2 = Subclass2()
> > let sc3 = Subclass3()
> >
> > let objects : [Superclass] = [sc1, sc2, sc3]
> >
> > for subclassObject in objects {
> > switch subclassObject {
> > case let object = subclassObject as? Subclass1:
> > doSomethingWith(object)
> > case let object = subclassObject as? Subclass2:
> > doSomethingWith(object)
> > case let object = subclassObject as? Subclass3:
> > doSomethingWith(object)
> > default:
> > return
> > }
> > }
> >
> > This gives an error, expecting a colon (:) after object on every case.
> >
> > I wanted to be sure I wasn't missing something in my syntax (nor some
> obvious-to-others reason this isn't supported) before going to swift
> evolution.
> >
> >
> > --
> > Nate Birkholz
> >
> > ___
> > swift-users mailing list
> > swift-users@swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
> >
> >
> > ___
> > swift-users mailing list
> > swift-users@swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
>
>
> --
> Rick Mann
> rm...@latencyzero.com
>
>
> ___
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
[swift-users] object.self?
I just saw a question which brought up something I didn't know about.
Apparently sometimes you have to call object.self in a place that looks like
you should just use "object." What does this usage mean?
for subclassObject in objects {
switch subclassObject.self {<--- Here, why not "subclassObject"
alone?
case is Subclass1:
doSomethingWith(subclassObject as! Subclass1)
case is Subclass2:
doSomethingWith(subclassObject as! Subclass2)
case is Subclass3:
doSomethingWith(subclassObject as! Subclass3)
default:
break
}
}
Thanks,
Rick
> On Jul 8, 2016, at 08:15 , Dan Loewenherz via swift-users
> wrote:
>
> To my knowledge, you can’t do exactly what you’re trying to do, but this is
> close:
>
> for subclassObject in objects {
> switch subclassObject.self {
> case is Subclass1:
> doSomethingWith(subclassObject as! Subclass1)
>
> case is Subclass2:
> doSomethingWith(subclassObject as! Subclass2)
>
> case is Subclass3:
> doSomethingWith(subclassObject as! Subclass3)
>
> default:
> break
> }
> }
>
> On Fri, Jul 8, 2016 at 10:11 AM, Nate Birkholz via swift-users
> wrote:
> This looks like it doesn't work (swift 2.x), but wanted to be sure it's not
> supported:
> class Superclass {}
> class Subclass1 : Superclass {}
> class Subclass2 : Superclass {}
> class Subclass3 : Superclass {}
>
> let sc1 = Subclass1()
> let sc2 = Subclass2()
> let sc3 = Subclass3()
>
> let objects : [Superclass] = [sc1, sc2, sc3]
>
> for subclassObject in objects {
> switch subclassObject {
> case let object = subclassObject as? Subclass1:
> doSomethingWith(object)
> case let object = subclassObject as? Subclass2:
> doSomethingWith(object)
> case let object = subclassObject as? Subclass3:
> doSomethingWith(object)
> default:
> return
> }
> }
>
> This gives an error, expecting a colon (:) after object on every case.
>
> I wanted to be sure I wasn't missing something in my syntax (nor some
> obvious-to-others reason this isn't supported) before going to swift
> evolution.
>
>
> --
> Nate Birkholz
>
> ___
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
> ___
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
--
Rick Mann
rm...@latencyzero.com
___
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