[英]How to correctly setup NSNotification and post?
我想为每个连接委托制作一个单独的Reachability观察者,但是我无法正确构建它,这里有一些代码片段。
MYReachability.m
static MYReachability *sharedInstance;
+ (MYReachability *)sharedInstance
{
if (sharedInstance == NULL) {
sharedInstance = [[MYReachability alloc] init];
}
return sharedInstance;
}
- (void)addReachabilityObserver
{
[[NSNotificationCenter defaultCenter] addObserver: self
selector: @selector(reachabilityChanged:)
name: kReachabilityChangedNotification
object: nil];
Reachability *reach = [Reachability reachabilityWithHostname: @"www.apple.com"];
[reach startNotifier];
}
- (void) reachabilityChanged: (NSNotification *)notification {
NSLog(@"notification: %@", notification);
Reachability *reach = [notification object];
if( [reach isKindOfClass: [Reachability class]]) {
NetworkStatus status = [reach currentReachabilityStatus];
NSLog(@"reachability status: %u", status);
if (status == NotReachable) {
// Insert your code here
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error"
message:@"Cannot connect to server..."
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[alert show];
}
}
}
在MYConnectionDelegate.m中
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
if (error.code) {
// sending notification to viewController
[[MYReachability sharedInstance] addReachabilityObserver];
MYTestClass *myTestClass = [MYTestClass new];
[myTestClass notificationTrigger];
}
}
在MYTestClass.m中
- (void)notificationTrigger
{
// All instances of TestClass will be notified
[[NSNotificationCenter defaultCenter]
postNotificationName:kReachabilityChangedNotification
object:self];
}
Rick,谢谢,这是有效的,但是这里有另一个问题,每次调用都会再生成一个堆栈通知......我在MYReachability.m中做了一个dealloc
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
但以前的通知仍然存在。
您正在调用方法notificationTrigger
但您的测试类只有方法notificationTrigger:
带冒号,即一个参数。
改变[myTestClass notificationTrigger];
to [myTestClass notificationTrigger:self];
它应该工作。
如果您只希望通知显示一次,请在显示警报视图后将自己移除为观察者,如下所示:
- (void) reachabilityChanged: (NSNotification *)notification {
NSLog(@"notification: %@", notification);
Reachability *reach = [notification object];
if( [reach isKindOfClass: [Reachability class]]) {
NetworkStatus status = [reach currentReachabilityStatus];
NSLog(@"reachability status: %u", status);
if (status == NotReachable) {
// Insert your code here
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Cannot connect to server..." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
}
}
在一个班级:
[[NSNotificationCenter defaultCenter] postNotificationName:@"notifyMe" object:self];
在另一个班级:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(doSomething)
name:@"notifyMe"
object:nil];
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