I'm trying to make an NSAccessibilityRadioButton element, but I'm getting ... let's say an unexpected error. Here is what I'm doing
I have a base class of NSAccessibilityElement:
class AccessibilityElementPrototype: NSAccessibilityElement {
.
.
.
}
I have another class, which should implement NSAccessibilityRadioButton protocol like this:
class AccessibilityElementTab: AccessibilityElementPrototype, NSAccessibilityRadioButton {
func accessibilityValue() -> NSNumber? {
...
}
}
The problem is that I'm getting the following error:
Method 'accessibilityValue()' with Objective-C selector 'accessibilityValue' conflicts with method 'accessibilityValue()' from superclass 'NSAccessibilityElement' with the same Objective-C selector
If someone has already encountered such a problem and has solution, please share.
I'm really happy you asked this, because I thought I was crazy.
It appears, unbelievably, that some of the NSAccessiblity protocols are broken in Swift. I've opened a bug with Apple, and I encourage you do the same. In the mean time, it's fairly easy to work around this, just inconvenient.
You can directly use NSView methods to achieve the same result:
view.setAccessibilityRole(...)
view.setAccessibilityElement(true)
#objc override func accessibilityValue() -> Any? {
...
}
Don't forget about setting the accessibiltyElement property to true. I didn't realize that was necessary at first, and couldn't figure out why nothing was showing up. Accessibility Inspector's Show Ignored Elements helped me there.
Something odd has started happening with a new Swift project I've created
You can see that I have a class called ViewController which is of type UIViewController
I have a function called someFunction that takes an input String? and give a String of "ABCDEFG". Simple right?
Well when I try to assign a class variable the output of that function you can see that autocomplete thinks someFunction requires (self: ViewController) input and it should instead take a String? input
Does anyone know what is happening here? It's driving me crazy
So it turns out I derped pretty hard.
I was trying to utilize a member only function from within a scope where the class hadn't been instantiated.
Instantiate your classes first kids...
I need to write a Spotlight Importer for an application that I've written in Swift, and am referring to the official Apple guide for Writing a Spotlight Importer.
It seems straightforward enough, however creating a Spotlight Importer project creates a default setup for an Objective-C implementation. Now, working with Objective-C isn't a huge problem (I've used it plenty of times in the past) but everything I've written for my application is in Swift, so I'd really I'd like to write the importer in Swift too to avoid switching between languages, and also so I can share some of the code that I've already done for reading/writing files.
Firstly, is it possible to write a Spotlight Importer using Swift instead of Objective-C? And if it is, where should I start (e.g- if I take the Objective-C starting point, what would I do to switch over to Swift instead)?
It took me a bit of time to get this to work.
Instead of adding Swift code to the mdimporter, I import an embedded framework already setup for my app.
I removed all the example code except main.c and GetMetadataForFile.m.
In the latter I import my framework where all the functionality now resides as Swift code.
The built mdimporter is added to the app.
In the File Inspector set Location to Relative to Build Products.
The app then adds the mdimporter with a Copy Files Build Phase.
Destination: Wrapper
Subpath: Contents/Library/Spotlight
The following needs to be added to the Run Search Paths build setting, as we are linking to the app's embedded frameworks.
#loader_path/../../../../../Frameworks
If you get compiler error that the framework module can't be found when building the app, depending on how your workspace is set up, you might need to modify your app's Scheme.
Turn off Parallelize Build
Add the Build targets in this sequence:
Frameworks project(s)
mdimporter project
App project
The additional benefit of having all the logic in a framework, is that it can be prototyped and verified in a Playground. A million times easier than debugging an mdimporter plugin.
Yes, it is possible to write a Spotlight Importer entirely* in Swift!
*except for a few lines of code in main.m
I've just published one here: https://github.com/foxglove/MCAPSpotlightImporter
Here's a detailed blog post about the implementation process:
https://foxglove.dev/blog/implementing-a-macos-search-plugin-for-robotics-data
The difficult part of this is implementing a plugin that's compatible with the CFPlugIn architecture. (The MDImporter-specific logic is relatively minimal.) The CFPlugIn API is based on Microsoft's COM and Apple's docs are almost 20 years old.
The plugin is expected to be a block of memory conforming to a certain memory layout — specifically, the first value in the block must be a pointer to a virtual function table (vtable) for the requested interface (in the case of a MDImporter, this is either MDImporterInterfaceStruct or MDImporterURLInterfaceStruct) or the base IUnknown interface. This layout is documented here.
I wanted to organize the Swift code into a class, but you can't control the memory layout of a Swift class instance. So I created a "wrapper" block of memory which holds the vtable and an unsafe pointer to the class instance. The class has a static func allocate() which uses UnsafeMutablePointer to allocate the wrapper block, create and store the class instance in it, and also initialize the vtable.
The vtable implements the standard COM base interface (IUnknown) functions (QueryInterface, AddRef, and Release) by grabbing the class instance out of the wrapper and calling the queryInterface(), addRef(), and release() methods on the instance. It also implements the Spotlight-specific ImporterImportURLData function (or ImporterImportData). Unfortunately, in my testing, it seemed like Spotlight did not pass the correct pointer to the wrapper struct as the first argument to ImporterImportURLData, so it was impossible to call a method on the class instance, so the function that actually imports attributes for a file had to be a global function. For this reason I wasn't able to make the plug-in implementation a more generic class that could be used with any interface — it has to be tied to a specific global importer function.
I'd encourage you to view the full source on GitHub, but in the interest of not being a link-only answer, here's the core functionality:
final class ImporterPlugin {
typealias VTable = MDImporterURLInterfaceStruct
typealias Wrapper = (vtablePtr: UnsafeMutablePointer<VTable>, instance: UnsafeMutableRawPointer)
let wrapperPtr: UnsafeMutablePointer<Wrapper>
var refCount = 1
let factoryUUID: CFUUID
private init(wrapperPtr: UnsafeMutablePointer<Wrapper>, factoryUUID: CFUUID) {
self.wrapperPtr = wrapperPtr
self.factoryUUID = factoryUUID
CFPlugInAddInstanceForFactory(factoryUUID)
}
deinit {
let uuid = UUID(factoryUUID)
CFPlugInRemoveInstanceForFactory(factoryUUID)
}
static func fromWrapper(_ plugin: UnsafeMutableRawPointer?) -> Self? {
if let wrapper = plugin?.assumingMemoryBound(to: Wrapper.self) {
return Unmanaged<Self>.fromOpaque(wrapper.pointee.instance).takeUnretainedValue()
}
return nil
}
func queryInterface(uuid: UUID) -> UnsafeMutablePointer<Wrapper>? {
if uuid == kMDImporterURLInterfaceID || uuid == IUnknownUUID {
addRef()
return wrapperPtr
}
return nil
}
func addRef() {
precondition(refCount > 0)
refCount += 1
}
func release() {
precondition(refCount > 0)
refCount -= 1
if refCount == 0 {
Unmanaged<ImporterPlugin>.fromOpaque(wrapperPtr.pointee.instance).release()
wrapperPtr.pointee.vtablePtr.deinitialize(count: 1)
wrapperPtr.pointee.vtablePtr.deallocate()
wrapperPtr.deinitialize(count: 1)
wrapperPtr.deallocate()
}
}
static func allocate(factoryUUID: CFUUID) -> Self {
let wrapperPtr = UnsafeMutablePointer<Wrapper>.allocate(capacity: 1)
let vtablePtr = UnsafeMutablePointer<VTable>.allocate(capacity: 1)
let instance = Self(wrapperPtr: wrapperPtr, factoryUUID: factoryUUID)
let unmanaged = Unmanaged.passRetained(instance)
vtablePtr.initialize(to: VTable(
_reserved: nil,
QueryInterface: { wrapper, iid, outInterface in
if let instance = ImporterPlugin.fromWrapper(wrapper) {
if let interface = instance.queryInterface(uuid: UUID(iid)) {
outInterface?.pointee = UnsafeMutableRawPointer(interface)
return S_OK
}
}
outInterface?.pointee = nil
return HRESULT(bitPattern: 0x8000_0004) // E_NOINTERFACE <https://github.com/apple/swift/issues/61851>
},
AddRef: { wrapper in
if let instance = ImporterPlugin.fromWrapper(wrapper) {
instance.addRef()
}
return 0 // optional
},
Release: { wrapper in
if let instance = ImporterPlugin.fromWrapper(wrapper) {
instance.release()
}
return 0 // optional
},
ImporterImportURLData: { _, mutableAttributes, contentTypeUTI, url in
// Note: in practice, the first argument `wrapper` has the wrong value passed to it, so we can't use it here
guard let contentTypeUTI = contentTypeUTI as String?,
let url = url as URL?,
let mutableAttributes = mutableAttributes as NSMutableDictionary?
else {
return false
}
var attributes: [AnyHashable: Any] = mutableAttributes as NSDictionary as Dictionary
// Call custom global function to import attributes
let result = importAttributes(&attributes, forFileAt: url, contentTypeUTI: contentTypeUTI)
mutableAttributes.removeAllObjects()
mutableAttributes.addEntries(from: attributes)
return DarwinBoolean(result)
}
))
wrapperPtr.initialize(to: (vtablePtr: vtablePtr, instance: unmanaged.toOpaque()))
return instance
}
}
Finally, I created an #objc class that exposes this allocate function to Obj-C, where I can call it from main.m, and return the pointer to the wrapper block from the factory function. This was necessary because I didn't want to use the unstable #_cdecl attribute to expose a Swift function directly to the plug-in loader.
#objc public final class PluginFactory: NSObject {
#objc public static func createPlugin(ofType type: CFUUID, factoryUUID: CFUUID) -> UnsafeMutableRawPointer? {
if UUID(type) == kMDImporterTypeID {
return UnsafeMutableRawPointer(ImporterPlugin.allocate(factoryUUID: factoryUUID).wrapperPtr)
}
return nil
}
}
// main.m
void *MyImporterPluginFactory(CFAllocatorRef allocator, CFUUIDRef typeID) {
return [PluginFactory createPluginOfType:typeID factoryUUID:CFUUIDCreateFromString(NULL, CFSTR("your plugin factory uuid"))];
}
See my blog post for more details.
Since Apple introduced Swift as a language to be perfectly compatible with any existing Objective-C project I would suggest you just start with whatever makes things easier for you.
If you know Swift best then nothing keeps you from using that – for whatever project you might want. If you want to follow a tutorial that was written for Objective-C and not updated for Swift yet, I think you have two choices (I'd personally recommend going for the second option for now):
Write the same logic written in Objective-C within the tutorial now in Swift from scratch (nearly everything possible in Objective-C is easily possible with Swift, too). For that you need to understand the basics of Objective-C and the corresponding syntax and features in Swift though.
Start with Objective-C to follow the tutorial and keep things easier at the beginning (no need to really understand the tutorials details). Then use the great possibility of mix and matching Swift code alongside Objective-C code to customize the code for your needs or to extend it with your own pre-existing classes.
More specifically on the second option:
If you want to write new classes just use Swift – you can perfectly use everything written in Objective-C from within Swift and vice versa. If you feel you need to change classes already written in Objective-C you have these options: Extend the class written in Objective-C with a new Swift class, re-write that specific file in Swift or just edit the Objective-C file directly.
To learn more on how to mix and match Swift code alongside Objective-C I recommend reading Apples official documentation. It's part of the free iBook "Using Swift with Cocoa and Objective-C" written by Apple engineers for developers.
Unfortunately Apple actually does seem to provide their template for a Spotlight Importer from within XCode for Objective-C only at the moment. Don't know why this is though – I can't see anything stopping them from supporting Swift. We should probably report this with Apples Bug Reporter to stress the fact that people are actually asking for this.
Hope I didn't overlook anything here, otherwise my answer will be pointless. ^^
UPDATE (request)
Here are some steps on where to begin to implement the first approach:
First create a Spotlight Importer project with the latest XCode version
– Create a new "Cocoa Touch" class named exactly the same as your pre-created main Objective-C classes (e.g. "MySpotlightImporter")
Choose Swift and "Create Bridging Header" when asked during class creation
– Re-implement the code written in the ObjC-MySpotlightImporter class within the Swift class (you might want to create a Cocoa App with Core Data support in Swift and Objective-C to get some idea of their differences)
– I'm not sure if you can rewrite the GetMetaDataFile.m in Swift, too, I couldn't figure that out in my test, so you maybe need to keep it around (for now)
– In case you receive any errors along the way that point to some missing configuration just search for the related files/classes in the projects "Build settings" and apply your changes there
I hope this helps to get you started and is specific enough. I tried to do the necessary changes myself in order to provide an example project in Swift but unfortunately I couldn't get it working in a limited time. You may want to consider providing your code publicly though (e.g. on GitHub with a link posted here) in case you decide to port it yourself so others can profit from this, too.
Good luck!
I'm a bit confused why my NSThread cannot be instantiated using a selector due to a runtime error
target does not implement selector (*** -[FileSearcher processFilesAsync:])
The function is defined like this
func processFilesAsync(#data: [String])
and the NSThread will be created this way:
NSThread(target: self, selector: "processFilesAsync:", object: itemsPerThread[i])
"itemsPerThread" is just a dictionary with a String-Array as values.
As far as I know this should work as the method I want to invoke defines an argument and the selector I pass into NSThread's init() method indicates that the target method expects exactly one argument.
I already tried using Swift's "Selector" type instead of only a string but this didn't work as well. I also tried to change the method's type from "[String]" to "AnyObject" which didn't work, too.
Does anybody have a clue what might be wrong?
All of the code above lies within the same class.
I'm using Xcode 6 Beta 5.
Edit
I figured out that is has to do something with the parameter. I implemented a dummy method without parameters and tried to set this as target and it worked. As soon as I modified it to use a parameter as well -> same as above.
Found it. All I had to do was to change the parameter's type from AnyObject to AnyObject?. It even works with specialised types (in my case [String]? instead of [String]).
Of course, because you can call it nil as parameter...
I'm trying to re-write a cocoapod's Objective-C delegate protocol in Swift. The cocoapod is MZTimerLabel and I'm trying to notify my View Controller when the timer has finished. Xcode tries to layout the correct syntax for me but I cannot quite understand what is is asking for. For example, when I am reading the example method I can't discern when it says timerLabel whether that means to type 'timerLabel' or if `timerLabel' is a placeholder for my instance of the MZTimerLabel.
It looks like the protocal is telling me to call on MZTimerLabel and then tell it what instance in my view controller to listen for (my instance is called brewingTimer, but I can't get the Swift Syntax right. Perhaps I should declare brewingTimer.delegate = self in my ViewDidLoad()?
-(void)timerLabel:(MZTimerLabel*)timerLabel finshedCountDownTimerWithTime:(NSTimeInterval)countTime {
//time is up, what should I do master?
}
My Swift attempt:
MZTimerLabel(timerLabel(brewingTimer, finshedCountDownTimerWithTime: 5)){
//What I want to do when the timer finishes
{self.startTimer.setTitle("Ok!", forState: .Normal)
}
I get the error "use of unresolved identifier 'timerLabel'"
I'm learning programming more or less from scratch with Swift as my first language so I'm constantly having to learn to read code "backwards" in Objective C to translate it over to Swift. Also, I don't understand what "countTime" is. I've read through all of the Swift documentation and have looked through guides for method's in Objective C, but seeing an example of an actual Objective C method written in Swift would be very helpful.
Your delegate function becomes in swift as
func timerLabel(timerLabel: AnyObject!, finshedCountDownTimerWithTime countTime: NSTimeInterval){
self.startTimer.setTitle("Ok!", forState: .Normal)
var yourTimerLabel = timerLabel as? MZTimerLabel //Downcast to MZTimerLabel
//Now you can use yourTimerLabel as instance of MZTimerLabel
}
Implement this in your viewController where you want to get notified.Also conform to protocol.
Here timerLabel is instance of MZTimerLabel
Also import your protocol to Swift Bridging Header