可可對象空閒計時器

Question

我想了解根據指定的空閒時間使對象失效的最佳方法。我有一個操縱桿對象，從下面的joystickAdded方法實例化時，會自動啓動一個NSTimer爲該實例：

操縱桿

idleTimer = [NSTimer scheduledTimerWithTimeInterval:300 target:self selector:@selector(invalidate) userInfo:nil repeats:YES]; 

這工作得很好，但我的操縱桿陣列犯規得到清理，因爲該方法當閒置時應該調用joystickRemoved，但我不知道如何調用它，或者如果NSTimer是最佳方式。

JoystickController

void joystickAdded(void *inContext, IOReturn inResult, void *inSender, IOHIDDeviceRef device) { 
    JoystickController *self = (__bridge JoystickController*)inContext; 
    IOHIDDeviceOpen(device, kIOHIDOptionsTypeNone); 

    // Filter events for joystickAction 
    NSMutableDictionary *dict = [[NSMutableDictionary alloc] init]; 
    [dict setObject:[NSNumber numberWithInt:kIOHIDElementTypeInput_Button] forKey:(NSString*)CFSTR(kIOHIDElementTypeKey)]; 
    IOHIDDeviceSetInputValueMatching(device, (__bridge CFDictionaryRef)(dict)); 

    // Register callback for action event to find the joystick easier 
    IOHIDDeviceRegisterInputValueCallback(device, joystickAction, (__bridge void*)self); 
    Joystick *js = [[Joystick alloc] initWithDevice:device]; 
    [[self joysticks] addObject:js]; 
} 

void joystickRemoved(void *inContext, IOReturn inResult, void *inSender, IOHIDDeviceRef device) { 
    // Find joystick 
    JoystickController *self = (__bridge JoystickController*)inContext; 
    Joystick *js = [self findJoystickByRef:device]; 

    if(!js) { 
     NSLog(@"Warning: No joysticks to remove"); 
     return; 
    } 

    [[self joysticks] removeObject:js]; 
    [js invalidate]; 
} 

void joystickAction(void *inContext, IOReturn inResult, void *inSender, IOHIDValueRef value) { 
    long buttonState; 

    // Find joystick 
    JoystickController *self = (__bridge JoystickController*)inContext; 
    IOHIDDeviceRef device = IOHIDQueueGetDevice((IOHIDQueueRef) inSender); 
    Joystick *js = [self findJoystickByRef:device]; 

    // Get button state 
    buttonState = IOHIDValueGetIntegerValue(value); 

    switch (buttonState) { 
     // Button pressed 
     case 1: { 
      // Reset joystick idle timer 
      [[js idleTimer] setFireDate:[NSDate dateWithTimeIntervalSinceNow:300]]; 
      break; 
     } 
     // Button released 
     case 0: 
      break; 
    } 
} 

Answer 1

你可以使用委託模式。

1）制定協議JoystickDelegate，聲明方法- (void)joystickInvalidated:(Joystick *)joystick。

2）JoystickController應該執行JoystickDelegate。實施該方法從陣列中刪除joystick。

3）Joystick界面以及在joystickAdded的Joystick每個初始化分配上js.delegateself最後做一個弱屬性調用delegate。

4）現在，每當invalidate被調用，只需調用delegate與self內Joystick：

[self.delegate joystickInvalidated:self];