[英]Cannot convert (Timer!) -> Void to ((CFRunLoopTimer?) ->Void)! - Converting NSTimer extension to Swift 3
[英]quitting a void method on a timer
我有一種與錄制視頻同時運行的方法。 當方法結束時,它將觸發其他方法的鏈,直到記錄結束為止。 我希望能夠按一個按鈕來提前停止錄制,同時也退出該方法。 我目前正在嘗試的方法是使用NSTimer來檢查是否仍在錄音,如果不是,它會停止播放音頻,還應該調用return來停止該方法。
-(void) method
{
self.stopTimer = [NSTimer scheduledTimerWithTimeInterval:.05 target:self selector:@selector(checkRecording) userInfo:nil repeats:YES];
// Stuff happens
}
-(void) checkRecording
{
if (isRecording == NO)
{
if (player.playing == YES)
{
[player stop];
}
return;
}
}
這將立即停止音頻,但是該方法將繼續運行直到完成。 它不會調用序列中的下一個方法,這是朝正確方向邁出的一步,但是我需要它立即停止。 我唯一的理論是,這是因為我沒有在要停止的實際方法中調用return,而是在其他方法中調用了方法,但是即使那樣,我也不確定如何解決該問題,因為就我而言知道計時器只能指向其他方法,而我不能僅僅告訴它我想要它在要停止的方法內部執行的操作。 如果這不是問題,那么我真的不確定為什么這行不通。
如果計時器有效,則可以使其無效(這將停止計時器)。
我不確定是否真的需要進行所有檢查(最后一行),但是我目前是這樣進行的:
if ( myTimer != nil && [myTimer isValid] )
{
[myTimer invalidate];
myTimer = nil;
}
編輯:
if ( [myTimer isValid] )
{
[myTimer invalidate];
myTimer = nil;
}
我唯一的理論是,因為我沒有在要停止的實際方法內調用return,而是在其他方法中調用return
你的理論是正確的。 return
結束其所在的函數或方法,別無其他。 它將當前函數的上下文彈出堆棧,然后將執行返回給調用函數。
我不太確定如何解決此問題,因為據我所知,計時器只能指向其他方法,而我不能僅僅告訴它我想要它在要停止的方法內部執行的操作
我們可以使用對象存儲狀態,並使用該狀態來控制程序的流程。 該狀態可以不斷更新和檢查。 對於需要響應該狀態的更改而取消的長時間運行的任務,必須與任務並行地更新狀態。 既然您說計時器可以停止音頻,但是method
中的工作沒有完成,所以我假設該method
已經異步執行了長時間運行的任務。
這需要在后台執行異步長時間運行的任務(或一系列任務),並有可能取消,這與NSOperation
和NSOperationQueue
類很好地匹配。
您可以通過實現方法或塊在NSOperation
對象中執行工作。 實現您的代碼,以檢查該操作是否在所有適當的時間都已取消,並在發生這種情況時立即提供援助。
下面是一個希望與您的用例匹配的示例。 它是在iOS應用程序“空應用程序”模板中創建的,所有內容都在應用程序委托中。 我們的應用程序代表跟蹤做出是否取消決定所需的狀態,並安排一個計時器以輪詢該狀態的更改。 如果確實確定應該取消,則將工作的實際取消委托給操作隊列及其操作。
#import "AppDelegate.h"
@interface AppDelegate ()
@property (nonatomic) BOOL shouldStop; // Analogous to your isRecording variable
@property (nonatomic, strong) NSOperationQueue *operationQueue; // This manages execution of the work we encapsulate into NSOperation objects
@end
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Typical app delegate stuff
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
// Start our long running method - analogous to method in your example
[self method];
return YES;
}
- (void)method
{
// allocate operation queue and set its concurrent operation count to 1. this gives us basic ordering of
// NSOperations. More complex ordering can be done by specifying dependencies on operations.
self.operationQueue = [[NSOperationQueue alloc] init];
self.operationQueue.maxConcurrentOperationCount = 1;
// We create three NSBlockOperations. They only sleep the thread a little while,
// check if they've been cancelled and should stop, and keep doing that for a few seconds.
// When they are completed (either through finishing normally or through being cancelled, they
// log a message
NSMutableArray *operations = [NSMutableArray array];
for (int i = 0; i < 3; i++) {
// Block operations allow you to specify their work by providing a block.
// You can override NSOperation to provide your own custom implementation
// of main, or start, depending. Read the documentation for more details.
// The principle will be the same - check whether one should cancel at each
// appropriate moment and bail out if so
NSBlockOperation *operation = [[NSBlockOperation alloc] init];
// For the "weak/strong dance" to avoid retain cycles
__weak NSBlockOperation *weakOperation = operation;
[operation addExecutionBlock:^{
// Weak/strong dance
NSBlockOperation *strongOperation = weakOperation;
// Here is where you'd be doing actual work
// Either in a block or in the main / start
// method of your own NSOperation subclass.
// Instead we sleep for some time, check if
// cancelled, bail out if so, and then sleep some more.
for (int i = 0; i < 300; i++) {
if ([strongOperation isCancelled]) {
return;
}
usleep(10000);
}
}];
// The completion block is called whether the operation is cancelled or not.
operation.completionBlock = ^{
// weak/strong dance again
NSBlockOperation *strongOperation = weakOperation;
NSLog(@"Operation completed, %@ cancelled.", [strongOperation isCancelled] ? @"WAS" : @"WAS NOT");
};
[operations addObject:operation];
}
// Set up a timer that checks the status of whether we should stop.
// This timer will cancel the operations if it determines it should.
[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(checkShouldKeepGoing:) userInfo:nil repeats:YES];
// Use GCD to simulate a stopped recording to observe how the operations react to that.
// Comment out to see the usual case.
double delayInSeconds = 5;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
self.shouldStop = YES;
});
// Add the operations to the operation queue, exeuction will start asynchronously from here.
[self.operationQueue addOperations:operations waitUntilFinished:NO];
}
// If we should stop, cancel the operations in the queue.
- (void)checkShouldKeepGoing:(NSTimer *)timer
{
if (self.shouldStop) {
NSLog(@"SHOULD STOP");
[timer invalidate];
[self.operationQueue cancelAllOperations];
}
}
@end
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