How to Display an Alert Controller When Nsdate == to a Time (For Example 12:00 Am) in Swift

How to display an Alert Controller when NSDate == to a time (for example 12:00 AM) in Swift?

Set a background timer to fire on or after the time you want to set:

class ViewController: UIViewController {
    var timer: NSTimer!

    func viewDidLoad() {
        let fireDate = NSCalendar.currentCalendar().dateWithEra(1, year: 2016, month: 6, day: 17, hour: 0, minute: 0, second: 0, nanosecond: 0)!
        self.timer = NSTimer(fireDate: fireDate, interval: 0, target: self, selector: #selector(ViewController.displayAlert), userInfo: nil, repeats: false)
        NSRunLoop.currentRunLoop().addTimer(self.timer, forMode: NSDefaultRunLoopMode)
    }

    func displayAlert() {
        let alertController = UIAlertController(title: "Timer fired", message: "Hey, timer is fired", preferredStyle: .Alert)
        let okAction = UIAlertAction(title: "OK", style: .Default, handler: nil)

        alertController.addAction(okAction)
        self.presentViewController(alertController, animated: false, completion: nil)
    }
}

How to update/display data (for example image) based on the time range?

Found the solution, when You are using calendar date components and using the switch for hour and minutes.

Launch a local notification at a specific time in iOS

Well in iOS 10 Apple has deprecated UILocalNotification which means it is time to get familiar with a new notifications framework.

Setup
This is a long post so let’s start easy by importing the new notifications framework:

// Swift
import UserNotifications

// Objective-C (with modules enabled)
@import UserNotifications;

You manage notifications through a shared UNUserNotificationCenter object:

// Swift
let center = UNUserNotificationCenter.current()

// Objective-C
UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];

Authorization
As with the older notifications framework you need to have the user’s permission for the types of notification your App will use. Make the request early in your App life cycle such as in application:didFinishLaunchingWithOptions:. The first time your App requests authorization the system shows the user an alert, after that they can manage the permissions from settings:

// Swift
let options: UNAuthorizationOptions = [.alert, .sound];

// Objective-C
UNAuthorizationOptions options = UNAuthorizationOptionAlert + UNAuthorizationOptionSound;

You make the actual authorization request using the shared notification center:

// Swift
center.requestAuthorization(options: options) { (granted, error) in
    if !granted {
        print("Something went wrong")
    }
}

// Objective-C
[center requestAuthorizationWithOptions:options
completionHandler:^(BOOL granted, NSError * _Nullable error) {
if (!granted) {
NSLog(@"Something went wrong");
}
}];

The framework calls the completion handler with a boolean indicating if the access was granted and an error object which will be nil if no error occurred.

Note: The user can change the notifications settings for your App at any time. You can check the allowed settings with getNotificationSettings. This calls a completion block asynchronously with a UNNotificationSettings object you can use to check the authorization status or the individual notification settings:

 // Swift
 center.getNotificationSettings { (settings) in
     if settings.authorizationStatus != .authorized {
         // Notifications not allowed
     }
 }

 // Objective-C
 [center getNotificationSettingsWithCompletionHandler:^(UNNotificationSettings * _Nonnull settings) {
 if (settings.authorizationStatus != UNAuthorizationStatusAuthorized) {
// Notifications not allowed
 }
 }];

Creating A Notification Request
A UNNotificationRequest notification request contains content and a trigger condition:

Notification Content

The content of a notification is an instance of the UNMutableNotificationContent with the following properties set as required:

title: String containing the primary reason for the alert.

subtitle: String containing an alert subtitle (if required)

body: String containing the alert message text

badge: Number to show on the app’s icon.

sound: A sound to play when the alert is delivered. Use UNNotificationSound.default() or create a custom sound from a file.
launchImageName: name of a launch image to use if your app is launched in response to a notification.

userInfo: A dictionary of custom info to pass in the notification
attachments: An array of UNNotificationAttachment objects. Use to include audio, image or video content.

Note that when localizing the alert strings like the title it is better to use localizedUserNotificationString(forKey:arguments:) which delays loading the localization until the notification is delivered.

A quick example:

 // Swift
 let content = UNMutableNotificationContent()
 content.title = "Don't forget"
 content.body = "Buy some milk"
 content.sound = UNNotificationSound.default()

 // Objective-C
 UNMutableNotificationContent *content = [UNMutableNotificationContent new];
 content.title = @"Don't forget";
 content.body = @"Buy some milk";
 content.sound = [UNNotificationSound defaultSound];

Notification Trigger

Trigger a notification based on time, calendar or location. The trigger can be repeating:

Time interval: Schedule a notification for a number of seconds later. For example to trigger in five minutes:

 // Swift
 let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 300, repeats: false)

 // Objective-C
 UNTimeIntervalNotificationTrigger *trigger =     [UNTimeIntervalNotificationTrigger triggerWithTimeInterval:300
                              repeats:NO];

Calendar: Trigger at a specific date and time. The trigger is created using a date components object which makes it easier for certain repeating intervals. To convert a Date to its date components use the current calendar. For example:

 // Swift
 let date = Date(timeIntervalSinceNow: 3600)
 let triggerDate = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)

 // Objective-C
 NSDate *date = [NSDate dateWithTimeIntervalSinceNow:3600];
 NSDateComponents *triggerDate = [[NSCalendar currentCalendar]   
          components:NSCalendarUnitYear +
          NSCalendarUnitMonth + NSCalendarUnitDay +
          NSCalendarUnitHour + NSCalendarUnitMinute +
          NSCalendarUnitSecond fromDate:date];

To create the trigger from the date components:

 // Swift
 let trigger = UNCalendarNotificationTrigger(dateMatching: triggerDate, repeats: false)

 // Objective-C
 UNCalendarNotificationTrigger *trigger = [UNCalendarNotificationTrigger triggerWithDateMatchingComponents:triggerDate
                                     repeats:NO];

To create a trigger that repeats at a certain interval use the correct set of date components. For example, to have the notification repeat daily at the same time we need just the hour, minutes and seconds:

 let triggerDaily = Calendar.current.dateComponents([hour, .minute, .second], from: date)
 let trigger = UNCalendarNotificationTrigger(dateMatching: triggerDaily, repeats: true)

To have it repeat weekly at the same time we also need the weekday:

 let triggerWeekly = Calendar.current.dateComponents([.weekday, .hour, .minute, .second], from: date)
 let trigger = UNCalendarNotificationTrigger(dateMatching: triggerWeekly, repeats: true)

Scheduling

With both the content and trigger ready we create a new notification request and add it to the notification center. Each notification request requires a string identifier for future reference:

 // Swift
 let identifier = "UYLLocalNotification"
 let request = UNNotificationRequest(identifier: identifier, content: content, trigger: trigger)

 center.add(request, withCompletionHandler: { (error) in
     if let error = error {
         // Something went wrong
     }
 })

 // Objective-C
 NSString *identifier = @"UYLLocalNotification";
 UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:identifier
                              content:content trigger:trigger]

 [center addNotificationRequest:request withCompletionHandler:^(NSError * _Nullable error) {
  if (error != nil) {
    NSLog(@"Something went wrong: %@",error);
  }
  }];

Make UIAlertView Button trigger function On Press

NOTE:

Important: UIAlertView is deprecated in iOS 8. (Note that UIAlertViewDelegate is also deprecated.) To create and manage alerts in iOS 8 and later, instead use UIAlertController with a preferredStyle of UIAlertControllerStyleAlert.

Please check this out tutorial

"deprecated" means???

Objectvie C

.h file

    @interface urViewController : UIViewController <UIAlertViewDelegate> {

.m file

// Create Alert and set the delegate to listen events
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Today's Entry Complete"
                                                message:@"Press OK to submit your data!"
                                               delegate:self
                                      cancelButtonTitle:nil
                                      otherButtonTitles:@"OK", nil];

// Set the tag to alert unique among the other alerts.
// So that you can find out later, which alert we are handling
alert.tag = 100;

[alert show];

//[alert release];

-(void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{

    // Is this my Alert View?
    if (alertView.tag == 100) {
        //Yes

    // You need to compare 'buttonIndex' & 0 to other value(1,2,3) if u have more buttons.
    // Then u can check which button was pressed.
        if (buttonIndex == 0) {// 1st Other Button

            [self submitData];

        }
        else if (buttonIndex == 1) {// 2nd Other Button

        }

    }
    else {
     //No
        // Other Alert View

    }

}

Swift

The Swifty way is to use the new UIAlertController and closures:

    // Create the alert controller
    let alertController = UIAlertController(title: "Title", message: "Message", preferredStyle: .Alert)

    // Create the actions
    let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) {
        UIAlertAction in
        NSLog("OK Pressed")
    }
    let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) {
        UIAlertAction in
        NSLog("Cancel Pressed")
    }

    // Add the actions
    alertController.addAction(okAction)
    alertController.addAction(cancelAction)

    // Present the controller
    self.presentViewController(alertController, animated: true, completion: nil)

UIAlertView first deprecated IOS 9

From iOS8 Apple provide new UIAlertController class which you can use instead of UIAlertView which is now deprecated, it is also stated in deprecation message:

UIAlertView is deprecated. Use UIAlertController with a preferredStyle
of UIAlertControllerStyleAlert instead

So you should use something like this

UIAlertController * alert = [UIAlertController
                alertControllerWithTitle:@"Title"
                                 message:@"Message"
                          preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction* yesButton = [UIAlertAction
                    actionWithTitle:@"Yes, please"
                              style:UIAlertActionStyleDefault
                            handler:^(UIAlertAction * action) {
                                //Handle your yes please button action here
                            }];

UIAlertAction* noButton = [UIAlertAction
                        actionWithTitle:@"No, thanks"
                                  style:UIAlertActionStyleDefault
                                handler:^(UIAlertAction * action) {
                                   //Handle no, thanks button                
                                }];

[alert addAction:yesButton];
[alert addAction:noButton];

[self presentViewController:alert animated:YES completion:nil];

UIAlertController won't display - In Swift

The problem is that by the time you call this following function:

present(alertController, animated: true, completion: nil)

your mail view controller is still visible. You have to make sure that the alertController is presented on the top of window hierarchy. In your example, you have the following window hierarchy:

+---------------------------+
| MailComposeViewController |
+---------------------------+
            ||
+---------------------------+
|  ContactUsViewController  |
+---------------------------+

What you should do instead is to dismiss the email view controller first. When that is done, show you alert view controller.

let alertController = UIAlertController(title: "test", message: "test", preferredStyle: .Alert)
let okButton = UIAlertAction(title: "Okay", style: .Default, handler: nil)
alertController.addAction(okButton)
controller.dismissViewControllerAnimated(true){ () -> Void in
     self.present(alertController, animated: true, completion: nil)   
}

Alternatively, you can also present your alertController on top of the MailComposeViewController, like so:

let alertController = UIAlertController(title: "test", message: "test", preferredStyle: .Alert)
let okButton = UIAlertAction(title: "Okay", style: .Default, handler: nil)
alertController.addAction(okButton)
controller.present(alertController, animated: true, completion: nil)

Add placeholder text inside UITextView in Swift?

Updated for Swift 4

UITextView doesn't inherently have a placeholder property so you'd have to create and manipulate one programmatically using UITextViewDelegate methods. I recommend using either solution #1 or #2 below depending on the desired behavior.

Note: For either solution, add UITextViewDelegate to the class and set textView.delegate = self to use the text view’s delegate methods.

---

Solution #1 - If you want the placeholder to disappear as soon as the user selects the text view:

First set the UITextView to contain the placeholder text and set it to a light gray color to mimic the look of a UITextField's placeholder text. Either do so in the viewDidLoad or upon the text view's creation.

textView.text = "Placeholder"
textView.textColor = UIColor.lightGray

Then when the user begins to edit the text view, if the text view contains a placeholder (i.e. if its text color is light gray) clear the placeholder text and set the text color to black in order to accommodate the user's entry.

func textViewDidBeginEditing(_ textView: UITextView) {
    if textView.textColor == UIColor.lightGray {
        textView.text = nil
        textView.textColor = UIColor.black
    }
}

Then when the user finishes editing the text view and it's resigned as the first responder, if the text view is empty, reset its placeholder by re-adding the placeholder text and setting its color to light gray.

func textViewDidEndEditing(_ textView: UITextView) {
    if textView.text.isEmpty {
        textView.text = "Placeholder"
        textView.textColor = UIColor.lightGray
    }
}

---

Solution #2 - If you want the placeholder to show whenever the text view is empty, even if the text view’s selected:

First set the placeholder in the viewDidLoad:

textView.text = "Placeholder"
textView.textColor = UIColor.lightGray

textView.becomeFirstResponder()

textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)

(Note: Since the OP wanted to have the text view selected as soon as the view loads, I incorporated text view selection into the above code. If this is not your desired behavior and you do not want the text view selected upon view load, remove the last two lines from the above code chunk.)

Then utilize the shouldChangeTextInRange UITextViewDelegate method, like so:

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {

    // Combine the textView text and the replacement text to
    // create the updated text string
    let currentText:String = textView.text
    let updatedText = (currentText as NSString).replacingCharacters(in: range, with: text)

    // If updated text view will be empty, add the placeholder
    // and set the cursor to the beginning of the text view
    if updatedText.isEmpty {

        textView.text = "Placeholder"
        textView.textColor = UIColor.lightGray

        textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)
    }

    // Else if the text view's placeholder is showing and the
    // length of the replacement string is greater than 0, set 
    // the text color to black then set its text to the
    // replacement string
     else if textView.textColor == UIColor.lightGray && !text.isEmpty {
        textView.textColor = UIColor.black
        textView.text = text
    }

    // For every other case, the text should change with the usual
    // behavior...
    else {
        return true
    }

    // ...otherwise return false since the updates have already
    // been made
    return false
}

And also implement textViewDidChangeSelection to prevent the user from changing the position of the cursor while the placeholder's visible. (Note: textViewDidChangeSelection is called before the view loads so only check the text view's color if the window is visible):

func textViewDidChangeSelection(_ textView: UITextView) {
    if self.view.window != nil {
        if textView.textColor == UIColor.lightGray {
            textView.selectedTextRange = textView.textRange(from: textView.beginningOfDocument, to: textView.beginningOfDocument)
        }
    }
}

Applications are expected to have a root view controller at the end of application launch

I had this same problem. Check your main.m. The last argument should be set to the name of the class that implements the UIApplicationDelegate protocol.

retVal = UIApplicationMain(argc, argv, nil, @"AppDelegate");

iOS SwiftUI: pop or dismiss view programmatically

This example uses the new environment var documented in the Beta 5 Release Notes, which was using a value property. It was changed in a later beta to use a wrappedValue property. This example is now current for the GM version. This exact same concept works to dismiss Modal views presented with the .sheet modifier.

import SwiftUI

struct DetailView: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        Button(
            "Here is Detail View. Tap to go back.",
            action: { self.presentationMode.wrappedValue.dismiss() }
        )
    }
}

struct RootView: View {
    var body: some View {
        VStack {
            NavigationLink(destination: DetailView())
            { Text("I am Root. Tap for Detail View.") }
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            RootView()
        }
    }
}

---

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