Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
On May 14, 2015, at 08:40 , William Squires wrote:
>
> I'd like to know how to properly write a value transformer in Swift.
Something like this, I expect:
> class StringNotNilTransformer: NSObject {
>
> static var transformedValueClass: AnyClass { return NSNumber.self }
> static let allowsReverseTransformation = false
>
> func transformedValue (value: AnyObject?) -> AnyObject? {
> if let string = value as? String {
> return NSNumber (bool: string != "");
> }
> return NSNumber (bool: false);
> }
> }
I only checked this in a playground, but I suspect the following slightly
simpler version would also work too:
> class StringNotNilTransformer: NSObject {
>
> static var transformedValueClass: AnyClass { return NSNumber.self }
> static let allowsReverseTransformation = false
>
> func transformedValue (value: AnyObject?) -> AnyObject? {
> if let string = value as? String {
> return string != "";
> }
> return false;
> }
> }
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Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
Thanks, I didn't even think of that, but yeah, it would be easier. Still, I'd
like to know how to properly write a value transformer in Swift.
On May 12, 2015, at 5:38 PM, Quincey Morris
wrote:
> On May 12, 2015, at 14:29 , William Squires wrote:
>>
>> class IsNotEmptyTransformer : NSValueTransformer
>> {
>> }
>>
>> but the example in the documentation is in ObjC, not Swift, and refers to
>> id, not to "Bool"s or "String"s. Hints, anyone?
>
> Using a value transformer at all seems like a poor choice, and using one in
> Swift seems even less desirable.
>
> If you are intent on using one, you’ll need to ask a more specific question.
> What ‘id’ are you referring to? If you’re talking about the transformed
> value, then you have to use an object — specifically NSNumber to represent a
> boolean value. IOW, for your use case, the transformer would transform
> between NSNumber and NSString.
>
> Surely it would be far easier, though, to do what you would do in a modern
> Obj-C app: use a derived property. Add a new property to the window
> controller:
>
> class MyWindowController : NSWindowController
> {
> dynamic var message: String
> dynamic var messageIsEmpty: Bool {return String == “”}
>
> and bind the button’s Enabled binding to the “messageIsEmpty” property.
> That’s not quite all, though, because as it stands, “messageIsEmpty” isn’t
> KVO-compliant, so you also need to add:
>
> static var keyPathsForValuesAffectingMessageIsEmpty: NSSet {return NSSet
> (object: "messageIsEmpty”)}
>
> (All code written in Mail, not tested.)
>
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Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
On May 12, 2015, at 22:19 , Uli Kusterer wrote: > > I think at least one of those should be “message” instead of “messageIsEmpty” > … ? Indeed — the second one. I’m also not absolutely sure that a computed static property will have the desired effect. It may have to be a static method. But perhaps they’re the same thing from the Obj-C point of view. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
On 13 May 2015, at 00:38, Quincey Morris
wrote:
> static var keyPathsForValuesAffectingMessageIsEmpty: NSSet {return NSSet
> (object: "messageIsEmpty”)}
I think at least one of those should be “message” instead of “messageIsEmpty” …
?
Cheers,
-- Uli Kusterer
“The Witnesses of TeachText are everywhere...”
http://zathras.de
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Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
On May 12, 2015, at 15:38 , Quincey Morris
wrote:
>
> dynamic var message: String
> dynamic var messageIsEmpty: Bool {return String == “”}
> static var keyPathsForValuesAffectingMessageIsEmpty: NSSet {return NSSet
> (object: "messageIsEmpty”)}
FWIW, a Swift-ier way to do this might be something like:
dynamic var message: String = "" {
didSet {messageIsEmpty = message == ""}
}
private(set) dynamic var messageIsEmpty: Bool = true
This is at the cost of actually storing the derived property value, though
that’s not likely to be a problem in window controller.
(Again, not tested.)
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Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
On May 12, 2015, at 14:29 , William Squires wrote:
>
> class IsNotEmptyTransformer : NSValueTransformer
> {
> }
>
> but the example in the documentation is in ObjC, not Swift, and refers to id,
> not to "Bool"s or "String"s. Hints, anyone?
Using a value transformer at all seems like a poor choice, and using one in
Swift seems even less desirable.
If you are intent on using one, you’ll need to ask a more specific question.
What ‘id’ are you referring to? If you’re talking about the transformed value,
then you have to use an object — specifically NSNumber to represent a boolean
value. IOW, for your use case, the transformer would transform between NSNumber
and NSString.
Surely it would be far easier, though, to do what you would do in a modern
Obj-C app: use a derived property. Add a new property to the window controller:
class MyWindowController : NSWindowController
{
dynamic var message: String
dynamic var messageIsEmpty: Bool {return String == “”}
and bind the button’s Enabled binding to the “messageIsEmpty” property. That’s
not quite all, though, because as it stands, “messageIsEmpty” isn’t
KVO-compliant, so you also need to add:
static var keyPathsForValuesAffectingMessageIsEmpty: NSSet {return NSSet
(object: "messageIsEmpty”)}
(All code written in Mail, not tested.)
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Re: Aggravation trying to implement NSValueTransformer subclasses in Swift
> On May 12, 2015, at 2:29 PM, William Squires wrote: > > but the example in the documentation is in ObjC, not Swift, and refers to id, > not to "Bool"s or "String"s. Hints, anyone? ‘id’ in Obj-C is ‘AnyObject’ in Swift. You’ll need to use the “as” or “as?” operator to type-cast it to NSNumber or NSString. You should also read Apple’s book on using Swift with Objective-C, because there’s a lot more to know before you get started. —Jens ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Aggravation trying to implement NSValueTransformer subclasses in Swift
I'm trying to make what should be a fairly simple value transformer. I need to
bind the Enabled state of a control (NSButton in this case, but it could be any
control) to the .isEmpty state of a string. I would think this a common enough
task that an existing value transformer would be supplied, but I guess not.
Unfortunately, the documentation only gives a sample in ObjC, but not Swift.
I have the following:
class MyWindowController : NSWindowController
{
dynamic var message: String
override var windowNibName: String
{
return "MyWindowController"
}
...
}
there's an NSTextField in the window, and it's value is bound to the "message"
variable with bindings; simple enough. There's also a button whose enabled
status I want controlled based on if the value of "message" is the empty
string, so I make:
class IsNotEmptyTransformer : NSValueTransformer
{
}
but the example in the documentation is in ObjC, not Swift, and refers to id,
not to "Bool"s or "String"s. Hints, anyone?
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