通知观察者集。
它们在保留观察者的情况下观察通知，并在调用 - dealloc 时自动从 NSNotificationCenter 中移除自身。
self.observer = [AQSApplicationDidBecomeActiveObserver observerWithBlock:^{
// Called when the app became active.
}];self.observer = [AQSApplicationWillResignActiveObserver observerWithBlock:^{
// Called when the app will resign active.
}];self.observer = [AQSApplicationUserDidTakeScreenshotObserver observerWithBlock:^{
// Called when the user took screenshot.
}];self.observer = [AQSApplicationDidReceiveMemoryWarningObserver observerWithBlock:^{
// Called when the application receive memory warning.
}];self.observer = [AQSNotificationObserver observerWithBlock:^(NSDictionary *userInfo, id object) {
// Called when "FooNotification" is posted.
} name:@"FooNotification"];或者使用对象：
self.observer = [AQSNotificationObserver observerWithBlock:^(NSDictionary *userInfo, id object) {
// Called when "FooNotification" with object: `someObject` is posted.
} name:@"FooNotification" object:someObject];The MIT License (MIT)
Copyright (c) 2014 AquaSupport
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.