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This article mainly introduces the example analysis of the behavioral observer mode in Python, which is very detailed and has certain reference value. Friends who are interested must finish it!

1. Observer model

The observer model must include the roles of "observer" and "observed", and there is a logical relationship between the observer and the observed. when the observed changes, the observer will observe such changes and respond accordingly. For example, business data is the observer, and the user interface is the observer.

In fact, the observer model is mostly an one-to-many relationship, in which multiple observer objects can observe a certain object at the same time.

The implementation idea of the observer pattern is that the core abstract class is used to manage all other classes that depend on it, and actively notify and update other classes when the core class changes.

Second, application scenarios

An abstract model has two aspects, one of which depends on the other. Encapsulate these aspects in separate objects so that they can be changed and reused independently.

The change of one object will lead to the change of one or more other objects, but we don't know how many objects will change, which can reduce the coupling between objects.

An object must notify other objects without knowing who those objects are.

You need to create a trigger chain in the system. The behavior of An object will affect B object, and the behavior of B object will affect C object. You can use observer mode to create a chained trigger mechanism.

Third, code example

When the number of customers is reduced to a threshold, sales will inform the factory to reduce production and human resources to start layoffs, and vice versa.

Class Observer: observer core class Salesperson "" def _ init__ (self): self._number = None self._department = [] @ property def number (self): return self._number @ number.setter def number (self) Value): self._number = value print ('current customers: {}' .format (self._number)) for obj in self._department: obj.change (value) print ('-') def notice (self) Department): "relevant departments" self._department.append (department) class Hr: "Observer category" Personnel Department def change (self, value): if value

20: print ("personnel change: expansion") else: print ("personnel is not affected") class Factory: "" Observer class, factory class "def change (self, value): if value

25: print ("production plan change: increase production") else: print ("production plan remains unchanged") if _ _ name__ = ='_ main__': observer = Observer () hr = Hr () factory = Factory () observer.notice (hr) observer.notice (factory) observer.number = 10 observer.number = 15 observer.number = 20 observer Number = 25 and above are all the contents of the article "sample Analysis of Behavioral Observer patterns in Python" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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