Hi friend,
In apple sample code: Metronome, it uses ViewController.m to init metronome swift class as in follow link:
And now I want to use swift ViewController.swift to replace all Objective C part within the sample code.
But I tried first to rewrite following code line with Swift but failed:
metronome = [[Metronome alloc] init];
the whole original Objective C sample code part as follows, please help, thanks!
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#import "ViewController.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIButton *button;
@property (weak, nonatomic) IBOutlet UITextField *barTextField;
@property (weak, nonatomic) IBOutlet UITextField *beatTextField;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSLog(@"Hello, Metronome!\n");
NSError *error = nil;
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory:AVAudioSessionCategoryAmbient error:&error];
if (error) {
NSLog(@"AVAudioSession error %ld, %@", error.code, error.localizedDescription);
}
[audioSession setActive:YES error:&error];
if (error) {
NSLog(@"AVAudioSession error %ld, %@", error.code, error.localizedDescription);
}
// if media services are reset, we need to rebuild our audio chain
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(handleMediaServicesWereReset:)
name:AVAudioSessionMediaServicesWereResetNotification
object:audioSession];
metronome = [[Metronome alloc] init];
metronome.delegate = self;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark- Actions
- (IBAction)buttonPressed:(UIButton*)sender {
// change the selected state thereby the button color and title
// toggle between Start & Stop
sender.selected = !sender.selected;
if (metronome.isPlaying) {
[metronome stop];
} else {
[metronome start];
}
}
#pragma mark- Delegate
- (void)metronomeTicking:(Metronome * _Nonnull)metronome bar:(int32_t)bar beat:(int32_t)beat {
dispatch_async(dispatch_get_main_queue(), ^{
self.barTextField.text = [NSString stringWithFormat:@"%d", bar];
self.beatTextField.text = [NSString stringWithFormat:@"%d", beat];
});
}
#pragma mark- AVAudioSession Notifications
// see https://developer.apple.com/library/content/qa/qa1749/_index.html
- (void)handleMediaServicesWereReset:(NSNotification *)notification
{
NSLog(@"Media services have reset...");
// tear down
metronome.delegate = nil;
metronome = nil;
self.button.selected = NO;
// re-create
metronome = [[Metronome alloc] init];
metronome.delegate = self;
NSError *error = nil;
[[AVAudioSession sharedInstance] setActive:YES error:&error];
if (error) {
NSLog(@"AVAudioSession error %ld, %@", error.code, error.localizedDescription);
}
}
@endOK, I translated it for you. This code compiles, but I haven't tested it. This is for a file "ViewController.swift", and you can delete both "ViewController.m" and "ViewController.h". Don't forget to re-connect the 3 outlets to the storyboard and hook up the button action! (Also, just to be safe, reselect the ViewController class for the view controller in the storyboard, using the Identity inspector.)
No guarantees that this is error-free!
import UIKit
import AVFoundation
class ViewController: UIViewController, MetronomeDelegate
{
@IBOutlet weak var button: UIButton?
@IBOutlet weak var barTextField: UITextField?
@IBOutlet weak var beatTextField: UITextField?
var metronome: Metronome!
override func viewDidLoad () {
super.viewDidLoad ()
print ("Hello, Metronome!\n");
let audioSession = AVAudioSession.sharedInstance ()
do {
try audioSession.setCategory (AVAudioSessionCategoryAmbient)
try audioSession.setActive (true)
}
catch {
print (error)
}
// if media services are reset, we need to rebuild our audio chain
NotificationCenter.default.addObserver (self,
selector: #selector (handleMediaServicesWereReset(_:)),
name: NSNotification.Name.AVAudioSessionMediaServicesWereReset,
object: audioSession)
metronome = Metronome ()
metronome.delegate = self
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
@IBAction func buttonPressed (sender: UIButton!) {
// change the selected state thereby the button color and title
// toggle between Start & Stop
sender.isSelected = !sender.isSelected
if metronome.isPlaying {
metronome.stop ()
}
else {
metronome.start ()
}
}
@objc func metronomeTicking (_ metronome: Metronome, bar: Int32, beat: Int32) {
DispatchQueue.main.async {
self.barTextField!.text = String (format: "%d", bar)
self.beatTextField!.text = String (format: "%d", beat)
}
}
// see https://developer.apple.com/library/content/qa/qa1749/_index.html
@objc func handleMediaServicesWereReset (_ notification: Notification) {
print("Media services have reset...")
// tear down
metronome.delegate = nil
metronome = nil
button!.isSelected = false
// re-create
metronome = Metronome ()
metronome.delegate = self
do {
try AVAudioSession.sharedInstance ().setActive (true)
}
catch {
print (error)
}
}
}
