• Clean Code – Chapter 6 Objects and Data Structures


    • Data Abstraction

      Hiding implementation

    • Data/Object Anti-Symmetry

      Objects hide their data behind abstractions and expose function that operate on that data. Data structure expose their data and hava no meaningful functions.

      Procedural code(code using data structure) makes it easy to add new functions without changing the existing data structures. OO code, on the other hand, makes it easy to add new classes without changing existing functions.

      Procedural code makes it hard to add new data structures because all functions must change. OO code makes it hard to add new functions because all the classes must change.

    • The Law of Demeter

      A module should not know about the innards of the objects it manipulates.

      A method f of a class C should only call the methods of these:

      • C
      • An object created by f
      • An object passed as an argument to f
      • An object held in an instance variable of C

      推荐一篇博文:笛米特法则详解,通过一个简单的代码示例解释了上述概念。

      • Train Wrecks

        Bad code:

        final String outputDir = ctxt.getOptions().getScratchDir().getAbsolutePath();

        Or

        Options opts = ctxt.getOptions();
        File scratchDir = opts.getScratchDir();
        final String outputDir = scratchDir.getAbsolutePath();

        Only used for data structures

        final String outputDir = ctxt.options.scratchDir.absolutePath;
      • Hybrids

        Avoid hybrid structures that are half object and half data structure.

      • Hiding Structure

        Tell an object to do something, not ask it about its internals.

    • Data Transfer Objects (DTO)

      The quintessential form of a data structure is a class with public variables and no functions.

      • Active Record

        Special form of DTO. Hava navigational methods like save and find.

        Typically direct translations from database tables, or other data sources.

  • 相关阅读:
    mysql导出表的数据,在导入
    oracle数据迁移到mysql
    mybatis-使用generator反向数据库表并生成dao和mapping映射
    SQLserver单表数据导入导出
    java内省
    java反射
    springmvc文件上传
    Dubbo学习笔记8:Dubbo的集群容错与负载均衡策略
    Dubbo学习笔记7:Dubbo增强SPI与SPI中扩展点自动包装的实现原理
    Dubbo学习笔记6:Dubbo整体框架分析
  • 原文地址:https://www.cnblogs.com/gumuyueying/p/cleancode-ch6.html
Copyright © 2020-2023  润新知