Here's a block type that I am defining in objective-c
typedef void (^arrayBlock)(NSArray *blockArray);
I have an objective-c class with a method that uses this as a return block
-(void)loadTimesWithSuccessBlock:(arrayBlock)successBlock;
When I try to use this method in Swift, this is what autocomplete gives me.
let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { ([AnyObject]!) -> Void in
//Where is blockArray?
}
I'm assuming that [AnyObject]! is supposed to be the NSArray. But I don't see how I'm supposed to get access to that variable?
If I were to use this method in Objective-C I get a result like this:
[timeClockLibrarian loadTimesWithSuccessBlock:^(NSArray *blockArray) {
//I can use the blockArray here :)
}];
[AnyObject]! is indeed only the type of the variable; autocomplete didn't name it. You just need to do something like (blockArray: [AnyObject]!).
let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { (blockArray: [AnyObject]!) -> Void in
// your code here
}
Write like this:
let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { blockArray in
doSomething(blockArray)
}
If you want to refer to weak self use this:
let timeClockLibrarian = HMFTimeClockLibrarian()
timeClockLibrarian.loadTimesWithSuccessBlock { [weak self] blockArray in
self?.doSomething(blockArray)
}
You may also want to get rid of implicit unwrapping. If so, specify nullability in Obj-C code:
typedef void (^arrayBlock)(nullable NSArray *blockArray);
Related
In a library called UIScrollView-InfiniteScroll (linked here) you can find this line of code in Classes/UIScrollView+InfiniteScroll.m:
static const void *kPBInfiniteScrollStateKey = &kPBInfiniteScrollStateKey;
How do I rewrite this line in Swift? Is it even possible?
It would have helped a lot should have you included the original comment
// Keys for values in associated dictionary
static const void *kPBInfiniteScrollStateKey = &kPBInfiniteScrollStateKey;
You can use associated objects like this in Swift, courtesy of erhatsezer https://gist.github.com/serhatsezer/4abe382229b001b37b1ee2f46e62b90f#file-productdetail-extension-swift
private var associateKey: Void?
extension ProductDetail {
var totalSumOfBasket: String? {
get {
return objc_getAssociatedObject(self, &associateKey) as? String
}
set {
objc_setAssociatedObject(self, &associateKey, newValue, .OBJC_ASSOCIATION_RETAIN)
}
}
}
Most basic way to do that its using https://swiftify.com tool. Easiest way to convert objc to swift.
Also for infinite scrollView best solution I found is https://github.com/rebeloper/DScrollview it's completely written in swift.
I got a ListView in SwiftUI and want to generate RowViews depending on a given property.
Therefore I want to check the property of the element in the ForEach loop.
Xcode does not recognize the type of the element, thats why i want to cast the element to the correct Class which is an NSManagedObject Subclass.
I created the NSManagedObject Subclass from the xcdatamodeld (Editor -> Create NSManagedObject Subclass...).
The NSManagedObject Subclass is created in objective-c and I added the .h file to the bridging header.
I have no problem working with the NSManagedObject Subclass in the rest of the project.
I can even create an property of that Type in the same Struct like so:
struct MyListView: View {
var test : MyNSManagedObjectSubclass //Xcode does recognize it here
For some reason Xcode wont recognize the NSManagedObject Subclass inside the ForEach Loop.
code looks like:
struct MyListView: View {
var test : MyNSManagedObjectSubclass //Xcode does recognize it here
#EnvironmentObject private var fetchResultsContainer : FetchedResultsContainer
var body: some View {
NavigationView{
VStack{
ForEach(fetchResultsContainer.results , id: \.identifier) { result in
if let castedResult = result as! MyNSManagedObjectSubclass { //Xcode does not recognize it here
if castedResult.property{
ResultRowView(input: result)
}
}
}
}
}
}
}
FetchedResultsContainer:
#objc class FetchedResultsContainer : NSObject, ObservableObject{
#objc #Published var results: [MyNSManagedObjectSubclass]()
#objc static let sharedInstance: FetchedResultsContainer = {
let instance = FetchedResultsContainer()
return instance
}()
}
I feel like im missing something obvious, as im still quite new to Swift and SwiftUI.
Appreciate your help.
Ok after taking a step back and simply coding it again from scratch it simply worked an no casting was needed...
List(fetchResultsContainer.results, id: \.identifier) { result in
if (result.property == 0) {
//do something
}
}
My assumption that the casting was not working was not correct.
I probably checked result.property == false, with property being of type NSNumber and it gave out some strange compile errors that led me on the wrong path.
I'm trying to get access to MKMapSnapshotter's private instance variables _lodpiSnapshotCreator and _hidpiSnapshotCreator in Swift on macOS.
Thanks to class-dump, I know they're there (see here):
#interface MKMapSnapshotter : NSObject
{
[...]
VKMapSnapshotCreator *_lodpiSnapshotCreator;
VKMapSnapshotCreator *_hidpiSnapshotCreator;
}
but no matter what I do, I can't get ahold of them.
This is how I checked whether I could access them or not:
let snapshotter = MKMapSnapshotter(options: snapshotOptions)
let varNames = ["_lodpiSnapshotCreator", "_hidpiSnapshotCreator"]
for varName in varNames {
if let testIVar = class_getInstanceVariable(MKMapSnapshotter.self, varName) {
if let test = object_getIvar(snapshotter, testIVar) as? VKMapSnapshotCreator {
print(test)
} else {
print("Got ivar, but \(varName) is still nil (getInstanceVariable)")
}
} else {
print("\(varName) is nil (getInstanceVariable)")
}
}
Curiously, class_getInstanceVariable doesn't return nil, but object_getIvar does.
Got ivar, but _lodpiSnapshotCreator is still nil (getInstanceVariable)
Got ivar, but _hidpiSnapshotCreator is still nil (getInstanceVariable)
I'm at my wit's end here. All I can find via Google is people recommending the use of class_getInstanceVariable (which I already use) and key-value-coding (which doesn't work at all).
This must have been done before. Can anyone help me out?
Edit: So far, I have tried this:
#interface MKMapSnapshotter() {
#public VKMapSnapshotCreator *_lodpiSnapshotCreator;
#public VKMapSnapshotCreator *_hidpiSnapshotCreator;
}
#end
That compiles successfully, but when trying to use it, Swift keeps insisting that the members _lodpiSnapshotCreator and _hidpiSnapshotCreator don't exist.
Since we don't have or control the source code we can't change the variables to properties. Just tried this works for your case:
extension MKMapSnapshotter {
func getPrivateVariable() -> String? {
return value(forKey: "_lodpiSnapshotCreator") as? String
}
open override func value(forUndefinedKey key: String) -> Any? {
if key == "_lodpiSnapshotCreator" {
return nil
}
return super.value(forUndefinedKey: key)
}
}
You can find more about this here.
If this does not work then I believe that there is no way to access Objective-C instance variables from Swift. Only Objective-C properties get mapped to Swift properties.
Hope this helps!!
My Swift enumeration is as below:
#objc enum NetworkError: Int, RawRepresentable {
case NoData
case Generic
func description() -> String {
switch self {
case .NoData: return "No data available"
case .Generic: return "Something goes wrong, please try again later"
}
}
}
My question is, how to call the description method from my Objective-C class. In Swift the call is as simple as:
NetworkError.Generic.description()
NetworkError.NoData.description()
Thanks
I don't think you can do this. If you look at the generated header the enum looks something like this to Objective-C:
typedef SWIFT_ENUM(NSInteger, NetworkError) {
NetworkErrorNoData = 0,
NetworkErrorGeneric = 1,
};
It's just a basic C style enum, it's not an object with methods, more info https://developer.apple.com/swift/blog/?id=22
I am creating a swift framework. In that one class is like this as shown below.
import Foundation
#objc public class classA: NSObject {
public override init (){
super.init();
}
/**
Singleton intance is returned.
*/
public class var sharedInstance: classA {
struct Static {
static let instance = popeye();
}
return Static.instance
}
}
Now when i add this framework into a Objective c project and try to access "sharedInstance" i get this error.
Property 'sharedInstance' not found on object of type ClassA.
Fix it Replace 'sharedInstance' with 'sharedInstance'
But even if i try use Fix it, this issue isnt solved.
NOTE: This issue doesn't happen when i integrate this framework with a swift project!!!
I AM STUCK.. :(
I tried to reproduce your problem. At first the syntax highlighter in Xcode flagged the same error in Objective-C that you mentioned, but the code actually was built and ran fine.
However, there is a cleaner way of doing this. In your code you are using a computed type property, which is evaluated every time you access it! You work around this by introducing the struct Static, where you essentially do what could be done in classA itself, like this:
/**
Singleton intance is returned.
*/
public static var sharedInstance: classA = popeye()
Here we used a stored type property, which is a recommended way to implement singletons, see here:
https://developer.apple.com/library/content/documentation/Swift/Conceptual/BuildingCocoaApps/AdoptingCocoaDesignPatterns.html
And here is some documentation on different kinds of properties:
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html
Finally i was able to fix this with a minor change !! :)
Swift framework code
#objc class SingletonTest: NSObject {
// swiftSharedInstance is not accessible from ObjC
class var swiftSharedInstance: SingletonTest {
struct Singleton {
static let instance = SingletonTest()
}
return Singleton.instance
}
// the sharedInstance class method can be reached from ObjC
class func sharedInstance() -> SingletonTest {
return SingletonTest.swiftSharedInstance
}
// Some testing
func testTheSingleton() -> String {
return "Hello World"
}
}
Objective C parent project code
SingletonTest *aTest = [SingletonTest sharedInstance];
NSLog(#"Singleton says: %#", [aTest testTheSingleton]);