可维护性杀手

1. Introduction

In this tutorial, we’ll discuss maintainability killers and explore the role of smells and heuristics in avoiding maintainability killers.

Smells and heuristics are two tools used in software development to improve maintainability. Smells are code-level indicators of problems with a system’s design or implementation that can lead to maintainability issues. On the other hand, heuristics are general principles for designing and implementing software known to lead to maintainable systems.

2. Maintainability and Maintainability Killers

Software development involves creating programs that are reliable, efficient, and maintainable. Maintainability is the characteristic of a software system that allows for easy modifications or updates to accommodate evolving requirements.

Maintainability is crucial for the long-term success of a software system. If a system is not maintainable, it can become difficult and expensive to modify, leading to technical debt, reduced reliability, and decreased efficiency.

2.1. Maintainability Killers

Maintainability killers refer to factors or elements in software development that negatively impact the ease of maintaining and updating a software system over time. These factors can make modifying, debugging, or extending the software challenging, leading to increased costs and reduced efficiency. Ultimately, maintainability killers can threaten the long-term success of a software project.

Common maintainability killers include:

1. Poor code quality: Code that is poorly written lacks proper commenting, and not following coding standards makes it difficult to maintain and update
2. Lack of documentation: Insufficient or outdated documentation can make understanding the software’s functionality and design challenging
3. Spaghetti code: Complex and tightly-coupled code with many interdependencies makes it difficult to modify or debug
4. Technical debt: Accruing technical debt through shortcuts or quick fixes can lead to a software system that is increasingly difficult to maintain over time
5. Insufficient testing: Poor or inadequate testing can make identifying and fixing issues challenging as the software evolves
6. Inadequate design patterns: Using design patterns not well suited to the problem can make it difficult to modify or extend the software
7. Lack of modularity: Tightly-coupled and monolithic software systems are often more difficult to update or modify without causing unintended side effects

3. Smells in Software Development

Code smells are warning signs in a software system’s design or implementation that suggest the presence of underlying problems. They often indicate that the system is not maintainable and may lead to technical debt or other issues if not addressed.
Code smells are indicators of suboptimal, questionable, or flawed code that may indicate deeper problems.

We must note that code smells are subjective and can vary based on the programming language, development methodologies, and team culture. However, identifying and addressing code smells can help improve the software’s quality, maintainability, and readability.

3.1. Examples of Code Smells

Some common code smells include:

1. Duplicate code: Repeated blocks of code that should be refactored into reusable functions or methods.
2. Long methods: Functions or methods that are overly complex and difficult to understand, maintain, and test.
3. Large classes: Overly complex classes, with too many methods, properties, and dependencies.
4. Switch statements: Complex control structures that are difficult to maintain and test.
5. Primitive obsession: Using low-level data types like integers, strings, or booleans instead of more appropriate abstractions.
6. Comments: Excessive or outdated comments that do not accurately reflect the code.
7. Magic numbers: Hard-coded numerical values that are used in multiple places and make it difficult to change them later.
8. God objects: Overly complex objects that have too many responsibilities and dependencies.
9. Feature envy: Methods that frequently use another object’s properties, indicating that the method should be part of that object.
10. Dead code: Unused or unnecessary code that is not being executed, but still increases the size and complexity of the software.

3.2. How to Identify and Remedy Code Smells

Code smells can be identified and remedied in several ways, including:

1. Code review: Having experienced developers review the code to identify code smells and suggest improvements
2. Automated tools: Using static analysis tools, such as linters or code quality checkers, to identify code smells and suggest fixes. E.g SonarQube, PMD, ESLint – a JavaScript linter, RuboCop
3. Refactoring: Restructuring the code to improve its quality, maintainability, and readability, such as breaking down large methods into smaller ones or refactoring duplicated code
4. Pair programming: Having two developers work together on the same code to improve its quality and identify code smells
5. Clean code practices: Following best practices for writing clean and maintainable code. This includes practices such as following encapsulating conditionals coding standards, using descriptive variable names, and writing well-commented code
6. Design patterns: Using well-established design patterns to structure the code and improve its modularity and maintainability
7. Test-driven development: Writing tests for the code before writing the code itself. This can help to identify code smells and improve the overall quality of the code

3.3. Example of Refactoring a Long Method

Let’s consider a function that takes numerical data and counts all values greater than zero, sums them up, and finally computes and print out their average.

Before refactoring:

function processData(data):
    // INPUT
    //     data = list of values
    // OUTPUT
    //     prints the average of positive values in data

    sum <- 0
    count <- 0 
    for value in data:
        if value > 0:
            sum <- sum + value
            count <- count + 1
    average <- sum / count
    print "Average:", average

After refactoring:

function processData(data):
    // INPUT
    //     data = list of values
    // OUTPUT
    //     prints the average of positive values in data

    sum <- getSumOfPositiveValues(data)
    count <- getCountOfPositiveValues(data)
    average <- sum / count
    print "Average:", average

function getSumOfPositiveValues(data):
    // Returns the sum of positive values in data

    sum <- 0 
    for value in data:
        if value > 0:
            sum <- sum + value
    return sum

function getCountOfPositiveValues(data):
    // Returns the count of positive values in data

    count <- 0
    for value in data:
        if value > 0:
            count <- count + 1
    return count

In this example, the long method (the initial function) has been refactored into three separate functions (or methods): , , and . This makes the code easier to understand, test, and maintain, as each function now has a clear responsibility and can be modified independently of the others.

4. Heuristics for Maintainable Software

Heuristics are rules of thumb that are used to guide software development and improve the maintainability of a software system.

4.1. Examples of Heuristics for Maintainable Software

Examples of heuristics for maintainable software include:

• KISS (Keep It Simple, Stupid): This heuristic suggests that software should be simple and easy to understand, rather than complex and difficult to maintain
• DRY (Don’t Repeat Yourself): This heuristic recommends avoiding code duplication and promoting code reusability whenever possible
• SOLID (Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion): This is a set of five principles that is a helpful guide to the design of maintainable software systems
• YAGNI (You Ain’t Gonna Need It): This heuristic advises developers not to add functionality that is not immediately required
• Single Responsibility Principle (SRP): This heuristic states that a software component should have only one reason to change, making it easier to understand and maintain
• Boy Scout Rule: This heuristic suggests that code should be left in a better state than when it was found, encouraging clean and organized code
• Occam’s Razor: This heuristic suggests that the simplest solution is usually the best, and complex solutions should only be used if necessary

5. The Role of Smells and Heuristics in Avoiding Maintainability Killers

First, let’s summarize the role of smells and heuristics:

In software development, it is crucial to focus on maintainability to ensure the long-term success of a project. Smells and heuristics play a critical role in avoiding maintainability killers by helping developers identify potential problems early on and taking steps to correct them.

These tools allow developers to focus on writing clean, readable, and well-structured code. This can improve the overall quality and maintainability of the codebase. By regularly using these tools, developers can ensure that their code remains maintainable over time, even as the codebase grows and evolves.

In the end, the goal is to build software that can scale and adapt to meet the changing needs of the business, while minimizing the time and resources required to maintain it. Thus, the use of smells and heuristics can be seen as a crucial step in avoiding maintainability killers and promoting software that is both robust and scalable.

6. Conclusion

In this article, we talked about three important terms in software development – maintainability killers, smells, and heuristics.

Maintainability killers are serious problems in code that make it difficult to maintain. While code smells are patterns in the code that indicate potential problems. On the other hand, Heuristics are guidelines used to identify these issues and improve the maintainability of the code.