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Is #MainActor just a syntactic sugar for DispatchQueue.main.async or else is there any other use to it?
If we take a look at the declarations for both UILabel and UIViewController, we can see that they’ve both been annotated with the new #MainActor attribute:
#MainActor class UILabel: UIView
#MainActor class UIViewController: UIResponder
What that means is that, when using Swift’s new concurrency system, all properties and methods on those classes (and any of their subclasses) will automatically be set, called, and accessed on the main queue. All those calls will automatically be routed through the system-provided MainActor, which always performs all of its work on the main thread — completely eliminating the need for us to manually call DispatchQueue.main.async.
Source: https://www.swiftbysundell.com/articles/the-main-actor-attribute/
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I wonder how the UIView.animate method works.
because just UI method must be used from main thread only?
try it
UIView.animate method was called without Dispatchqueue.main.async
so, I check Thread.isMainthread in UIView.animate result -> main
I think that because UIView use #MainActor annotation
But, Is there any counter case where #MainActor doesn't guarantee the main thread?
Questions
Why does the main thread guarantee the UIView.animate method?
Is my guess correct?
if my guess correct {
2-1. Is there any counter case where #MainActor doesn't guarantee the main thread?
}
The main thread guarantees the UIView.animate method because it manipulates UI elements, which should only be done on the main thread to ensure thread safety and avoid unexpected behavior.
Your guess is partially correct. The #MainActor attribute is used to mark methods that must be executed on the main thread. However, there may be cases where the attribute is not used correctly or where it does not fully guarantee that the method is executed on the main thread. For example, if a method marked with #MainActor calls another method that is not marked as such, or if a method is marked with #MainActor but also includes asynchronous code that is not properly managed, it could result in the method being executed on a background thread. Therefore, it's important to use #MainActor carefully and ensure that all related code is properly managed to avoid potential issues.
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import UIKit
import Foundation
open class podview: UIView {
open var strk = UIColor.black
.
.
}
I have to change the value of "strk" from another view controller. Is it possible to do it.
YES, You can do it. There are two way to do this.
Local Notification (NSNotification)
NSNotificationCenter addObserver in Swift
Delegatation
Examples of Delegates in Swift
If you want to Change View controller B Value from View controller A then you can directly access to it.
For EX ViewcontrollerB.yourVariable = Assign value - From View Controller A
Please review and understand both concepts.
Happy Coding..:)
I'm just providing you trick.
Yes you can change it. First you need to import model of the pod.
then you need to create object of the podview and then you will be able to access strk like
objectOfPodView.strk
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I have an Objective-C project, and need hints on how to call a ViewController which is in Swift from another controller in Objective-C?
Apparently it's quite easy.
You have to first make sure you're prepending your class declaration with #objc so that it's available to your Objective-C ones.
For example:
import Foundation
// Belongs to target 'TestProject'
#objc class SwiftController: UIViewController {
//... truncated
}
Now you simply have to import the name of your target (that the swift controller belongs to), appended with '-Swift.h'—exposing its interface—like so:
#import "TestProject-Swift.h"
Create a new file "YourAppName-Bridging-Header.h" and in this file you have to import "Your objective-C view controller.h"
Go to Build setting and search for bridging header and link with your birdging-header path.
Now you are able to write code in swift as usual.
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When I create a new file in Xcode I can specify a subclass of my new class. But when it is already created, how can I know which subclass has it?
Thanks.
You see that in the class definition / .h file, for example:
#interface BCFrequencyPlot : NSView
BCFrequencyPlot is a subclass of NSView.
During compilation, you can type:
po [self class]
It will show you class of self. You can check class for any object currently in scope.
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I'm using blocks inside a NSOperation. The main method of my NSOperation looks like this:
- (void) main {
[self callMethodOfALiraryUsingCompletionBlock:^() {
//this method takes time to execute, will call this block when done
}];
}
I'd like my NSOperationto terminate when what's inside the block is done. Currently, it returns directly, before what's inside the block is executed ... Any idea how I can solve this ?
Little detail in your question, here is one possible outline which may help:
Create a semaphore (dispatch_semaphore_create)
Execute your library code asynchronously (dispatch_async)
Have the completion block for your library code signal the semaphore
Have your main method wait on the semaphore
HTH