Sự định nghĩa. Mẫu đơn là một mẫu thiết kế hạn chế việc khởi tạo một lớp cho một đối tượng
Bây giờ chúng ta hãy xem các triển khai khác nhau của mẫu Thiết kế Singleton.
Phương pháp 1. Mẫu thiết kế Monostate/Borg Singleton
Hành vi của Singleton có thể được thực hiện theo mẫu của Borg nhưng thay vì chỉ có một thể hiện của lớp, có nhiều thể hiện có cùng trạng thái. Ở đây chúng tôi không tập trung vào việc chia sẻ danh tính cá thể thay vào đó chúng tôi tập trung vào trạng thái chia sẻ.
Python3
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đầu ra.
A1 : __main__.X object at 0x02EA2590 A2 : __main__.X object at 0x02EA2590 B1 : __main__.Y object at 0x02EA25B0 B2 : __main__.Y object at 0x02EA25B02
Singleton-Design-pattern
Khóa kiểm tra kép Mẫu thiết kế Singleton
Dễ dàng nhận thấy rằng khi một đối tượng được tạo, việc đồng bộ hóa luồng không còn hữu ích nữa vì bây giờ đối tượng sẽ không bao giờ bằng Không và bất kỳ chuỗi thao tác nào cũng sẽ dẫn đến kết quả nhất quán.
Vì vậy, khi đối tượng bằng Không, thì chỉ khi đó chúng ta mới có được Khóa trên phương thức getInstance.
Python3
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đầu ra.
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Tạo một singleton trong Python
Trong triển khai cổ điển của mẫu Thiết kế Singleton, chúng tôi chỉ cần sử dụng phương thức tĩnh để tạo phương thức getInstance có khả năng trả về tài nguyên được chia sẻ. Chúng tôi cũng sử dụng cái gọi là Trình xây dựng riêng ảo để tăng ngoại lệ chống lại nó mặc dù nó không bắt buộc lắm
Chúng ta có thể khởi tạo một đối tượng đơn lẻ không?
Nếu bạn có một đối tượng thông thường mà bạn không thể khởi tạo lại thì đó là vấn đề về bộ nhớ. Singleton không có gì khác biệt, ngoại trừ việc bạn phải viết một hàm để làm điều đó . Singletons phải hoàn toàn tự quản lý. Điều này có nghĩa là từ init đến deinit.
Bạn có thể tạo một singleton trong Python không?
Mẫu Singleton trong python là một mẫu thiết kế cho phép bạn chỉ tạo một phiên bản của một lớp trong suốt vòng đời của chương trình . Sử dụng một mẫu đơn có nhiều lợi ích. một vài trong số họ là. Để giới hạn quyền truy cập đồng thời vào một tài nguyên được chia sẻ.
Singleton có cần thiết trong Python không?
Singleton là ứng cử viên sáng giá nhất khi đáp ứng các yêu cầu sau. Kiểm soát quyền truy cập đồng thời vào tài nguyên được chia sẻ . Nếu bạn cần một điểm truy cập toàn cầu cho tài nguyên từ nhiều phần hoặc các phần khác nhau của hệ thống . Khi bạn chỉ cần có một đối tượng .
Singleton hoạt động như thế nào trong Python?
Singleton là một mẫu thiết kế sáng tạo, đảm bảo rằng chỉ có một đối tượng cùng loại tồn tại và cung cấp một điểm truy cập duy nhất vào đối tượng đó cho bất kỳ mã nào khác. Singleton has almost the same pros and cons as global variables. Although they're super-handy, they break the modularity of your code.