--cocoa Touch design mode and application notification mechanism, "learning swift from scratch" study notes (Day)

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Notification ( Notification ) mechanism is based on the viewer ( Observer ) mode is also called publishing / Subscription ( Publish/subscribe ) mode, is MVC ( Model - View - Controller) is an important part of the model.  

Questions raised

The weather has been a subject of great interest to the British, and the changes in recent years have become a subject of great concern to the Chinese people. I will decide whether to take the subway or drive to work according to the weather forecast, and my daughter will decide which dress to wear tomorrow according to the weather forecast. So I customized the weather forecast SMS Notification service for my phone in mobile company, it's working model.

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Every day the meteorological Bureau sends the weather forecast information to the mobile operator, and the mobile operator's SMS Center sends the weather report to the phone that has customized the service.

In a software system, an object state change can also affect the state of many other objects. There are many design schemes that can achieve this need, but the observer pattern is the most suitable one for the reusable and anonymous communication between objects .

Solution Solutions

The notification mechanism can implement communication between "one-to-many" objects. , all objects that are interested in a notification in the notification mechanism can be recipients. First, these objects need to send addobserver messages to notification hubs (nsnotificationcenter) for registration notifications, Postnotificationname Message Delivery notification to the notification center, the notification center will broadcast the notification to registered recipients. All the recipients don't know who delivered the notification, and they don't care more about its details. The delivery object is a one-to-many relationship with the receiver. If the recipient is no longer concerned about the notification, the Notification center will be issued a removeobserver message cancellation notification, no longer receive notifications.

  

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--cocoa Touch design mode and application notification mechanism, "learning swift from scratch" study notes (Day)