气味代码与重构

2019-01-22 本文已影响0人鹿特丹的风

整理自：https://sourcemaking.com/refactoring/smells

类型一：Bloaters

代码、方法和类增长到庞大的量。

Long Method

一般来说，长于10行的方法就应该考虑是否需要重构。如果方法中有些地方需要注释，就应该考虑是否把这些代码放入新方法内，即使该代码只有一行，原因是如果方法名是描述性的，就不需要阅读进行实际操作的源码。

解决方案：

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Replace Temp with Query

例如：

double calculateTotal() {
  double basePrice = quantity * itemPrice;
  if (basePrice > 1000) {
    return basePrice * 0.95;
  }
  else {
    return basePrice * 0.98;
  }
}

改为

double calculateTotal() {
  if (basePrice() > 1000) {
    return basePrice() * 0.95;
  }
  else {
    return basePrice() * 0.98;
  }
}
double basePrice() {
  return quantity * itemPrice;
}

Introduce Parameter Object

Preserve Whole Object

例如：

int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);

改为

boolean withinPlan = plan.withinRange(daysTempRange);

Replace Method with Method Object

例如：

class Order {
  //...
  public double price() {
    double primaryBasePrice;
    double secondaryBasePrice;
    double tertiaryBasePrice;
    // long computation.
    //...
  }
}

改为

class Order {
  //...
  public double price() {
    return new PriceCalculator(this).compute();
  }
}

class PriceCalculator {
  private double primaryBasePrice;
  private double secondaryBasePrice;
  private double tertiaryBasePrice;
  
  public PriceCalculator(Order order) {
    // copy relevant information from order object.
    //...
  }
  
  public double compute() {
    // long computation.
    //...
  }
}

Decompose Conditional

例如：

if (date.before(SUMMER_START) || date.after(SUMMER_END)) {
  charge = quantity * winterRate + winterServiceCharge;
}
else {
  charge = quantity * summerRate;
}

改为

if (isSummer(date)) {
  charge = summerCharge(quantity);
}
else {
  charge = winterCharge(quantity);
}

Large Class

一个包含了很多字段/方法/代码行的类。

解决方案：

Extract Class

When one class does the work of two, awkwardness results.

Extract Subclass

A class has features that are used only in certain cases.

Extract Interface

Multiple clients are using the same part of a class interface. Another case: part of the interface in two classes is the same.

Duplicate Observed Data

Is domain data stored in classes responsible for the GUI?

Primitive Obsession

用primitive field而不是small object代表简单事物；用常数来表示信息等。

解决方案：

Replace Data Value with Object

A class (or group of classes) contains a data field. The field has its own behavior and associated data.

Introduce Parameter Object

Preserve Whole Object

例如：

int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);

改为

boolean withinPlan = plan.withinRange(daysTempRange);

Replace Type Code with Class

A class has a field that contains type code. The values of this type are not used in operator conditions and do not affect the behavior of the program.

Replace Type Code with Subclasses

You have a coded type that directly affects program behavior (values of this field trigger various code in conditionals).

Replace Array with Object

例如：

String[] row = new String[2];
row[0] = "Liverpool";
row[1] = "15";

改为

Performance row = new Performance();
row.setName("Liverpool");
row.setWins("15");

Long Parameter List

一个方法包含了三个或四个以上的参数。

解决方案：

Replace Parameter with Method Call

例如：

int basePrice = quantity * itemPrice;
double seasonDiscount = this.getSeasonalDiscount();
double fees = this.getFees();
double finalPrice = discountedPrice(basePrice, seasonDiscount, fees);

改为

int basePrice = quantity * itemPrice;
double finalPrice = discountedPrice(basePrice);

Preserve Whole Object

例如：

int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);

改为

boolean withinPlan = plan.withinRange(daysTempRange);

Introduce Parameter Object

Data Clumps

不同部分的代码都包含了相同的一堆变量（即数据块）。如果要确定某些数据是否为数据块，只需删除其中一个数据值，然后查看其他值是否仍然有意义。如果不是，表明这组变量应该组合成一个对象。

Extract Class

When one class does the work of two, awkwardness results.

Introduce Parameter Object

Preserve Whole Object

例如：

int low = daysTempRange.getLow();
int high = daysTempRange.getHigh();
boolean withinPlan = plan.withinRange(low, high);

改为

boolean withinPlan = plan.withinRange(daysTempRange);

类型二：Object-Orientation Abusers

对OOP法则的不完整或是不正确的运用。

Switch Statements

存在复杂的switch操作或是一系列if语句。

解决方案：

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Move Method

A method is used more in another class than in its own class.

Replace Type Code with Subclasses

You have a coded type that directly affects program behavior (values of this field trigger various code in conditionals).

Replace Conditional with Polymorphism

例如：

class Bird {
  //...
  double getSpeed() {
    switch (type) {
      case EUROPEAN:
        return getBaseSpeed();
      case AFRICAN:
        return getBaseSpeed() - getLoadFactor() * numberOfCoconuts;
      case NORWEGIAN_BLUE:
        return (isNailed) ? 0 : getBaseSpeed(voltage);
    }
    throw new RuntimeException("Should be unreachable");
  }
}

改为

abstract class Bird {
  //...
  abstract double getSpeed();
}

class European extends Bird {
  double getSpeed() {
    return getBaseSpeed();
  }
}
class African extends Bird {
  double getSpeed() {
    return getBaseSpeed() - getLoadFactor() * numberOfCoconuts;
  }
}
class NorwegianBlue extends Bird {
  double getSpeed() {
    return (isNailed) ? 0 : getBaseSpeed(voltage);
  }
}

// Somewhere in client code
speed = bird.getSpeed();

Replace Parameter with Explicit Methods

例如：

void setValue(String name, int value) {
  if (name.equals("height")) {
    height = value;
    return;
  }
  if (name.equals("width")) {
    width = value;
    return;
  }
  Assert.shouldNeverReachHere();
}

改为

void setHeight(int arg) {
  height = arg;
}
void setWidth(int arg) {
  width = arg;
}

Introduce Null Object

例如：

if (customer == null) {
  plan = BillingPlan.basic();
}
else {
  plan = customer.getPlan();
}

改为

class NullCustomer extends Customer {
  boolean isNull() {
    return true;
  }
  Plan getPlan() {
    return new NullPlan();
  }
  // Some other NULL functionality.
}

// Replace null values with Null-object.
customer = (order.customer != null) ?
  order.customer : new NullCustomer();

// Use Null-object as if it's normal subclass.
plan = customer.getPlan();

Temporary Field

字段只在某些情况下被赋值，而在剩下的情况下，都不会被赋值。

解决方案：

Extract Class

When one class does the work of two, awkwardness results.

Replace Method with Method Object

例如：

class Order {
  //...
  public double price() {
    double primaryBasePrice;
    double secondaryBasePrice;
    double tertiaryBasePrice;
    // long computation.
    //...
  }
}

改为

class Order {
  //...
  public double price() {
    return new PriceCalculator(this).compute();
  }
}

class PriceCalculator {
  private double primaryBasePrice;
  private double secondaryBasePrice;
  private double tertiaryBasePrice;
  
  public PriceCalculator(Order order) {
    // copy relevant information from order object.
    //...
  }
  
  public double compute() {
    // long computation.
    //...
  }
}

Introduce Null Object

例如：

if (customer == null) {
  plan = BillingPlan.basic();
}
else {
  plan = customer.getPlan();
}

改为

class NullCustomer extends Customer {
  boolean isNull() {
    return true;
  }
  Plan getPlan() {
    return new NullPlan();
  }
  // Some other NULL functionality.
}

// Replace null values with Null-object.
customer = (order.customer != null) ?
  order.customer : new NullCustomer();

// Use Null-object as if it's normal subclass.
plan = customer.getPlan();

Refused Bequest

如果子类仅使用从其父项继承的某些方法和属性，则说明使用这种层次结构是不合适的。

解决方案：

Replace Inheritance with Delegation

You have a subclass that uses only a portion of the methods of its superclass (or it’s not possible to inherit superclass data).

Extract Superclass

You have two classes with common fields and methods.

Alternative Classes with Different Interfaces

两个类的功能几乎一样只是方法名不同。

Rename Method

The name of a method does not explain what the method does.

Move Method

A method is used more in another class than in its own class.

Add Parameter

A method does not have enough data to perform certain actions.

Parameterize Method

Multiple methods perform similar actions that are different only in their internal values, numbers or operations.

Extract Superclass

You have two classes with common fields and methods.

类型三：Change Preventers

如果你需要在代码中的某个位置更改某些内容，则必须在其他位置进行许多更改。

Divergent Change

当对某个类进行更改时，你发现自己必须更改许多不相关的方法。

解决方案：

Extract Class

When one class does the work of two, awkwardness results.

Extract Superclass

You have two classes with common fields and methods.

Extract Subclass

A class has features that are used only in certain cases.

Shotgun Surgery

进行任何修改都需要对许多不同的类进行许多小的更改。

解决方案：

Move Method

A method is used more in another class than in its own class.

Move Field

A field is used more in another class than in its own class.

Inline Class

A class does almost nothing and is not responsible for anything, and no additional responsibilities are planned for it.

Parallel Inheritance Hierarchies

每当为类创建子类时，你发现自己需要为另一个类创建子类。

解决方案：

Move Method

A method is used more in another class than in its own class.

Move Field

A field is used more in another class than in its own class.

类型四：Dispensables

指毫无意义或是不必要的东西，将其移除会使代码更清晰，更有效，更容易理解。

Comments

方法里面充满了解释性注释。

解决方案：

Extract Variable

例如：

void renderBanner() {
  if ((platform.toUpperCase().indexOf("MAC") > -1) &&
       (browser.toUpperCase().indexOf("IE") > -1) &&
        wasInitialized() && resize > 0 )
  {
    // do something
  }
}

改为

void renderBanner() {
  final boolean isMacOs = platform.toUpperCase().indexOf("MAC") > -1;
  final boolean isIE = browser.toUpperCase().indexOf("IE") > -1;
  final boolean wasResized = resize > 0;

  if (isMacOs && isIE && wasInitialized() && wasResized) {
    // do something
  }
}

解决方案：

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Rename Method

The name of a method does not explain what the method does.

Introduce Assertion

例如：

double getExpenseLimit() {
  // should have either expense limit or a primary project
  return (expenseLimit != NULL_EXPENSE) ?
    expenseLimit:
    primaryProject.getMemberExpenseLimit();
}

改为

double getExpenseLimit() {
  Assert.isTrue(expenseLimit != NULL_EXPENSE || primaryProject != null);

  return (expenseLimit != NULL_EXPENSE) ?
    expenseLimit:
    primaryProject.getMemberExpenseLimit();
}

Duplicate Code

两个或多个代码片段看起来几乎相同。

解决方案：

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Pull Up Field

Two classes have the same field.

Pull Up Constructor Body

例如：

class Manager extends Employee {
  public Manager(String name, String id, int grade) {
    this.name = name;
    this.id = id;
    this.grade = grade;
  }
  //...
}

改为

class Manager extends Employee {
  public Manager(String name, String id, int grade) {
    super(name, id);
    this.grade = grade;
  }
  //...
}

Form Template Method

Your subclasses implement algorithms that contain similar steps in the same order.

Substitute Algorithm

例如：

String foundPerson(String[] people){
  for (int i = 0; i < people.length; i++) {
    if (people[i].equals("Don")){
      return "Don";
    }
    if (people[i].equals("John")){
      return "John";
    }
    if (people[i].equals("Kent")){
      return "Kent";
    }
  }
  return "";
}

改为

String foundPerson(String[] people){
  List candidates =
    Arrays.asList(new String[] {"Don", "John", "Kent"});
  for (int i=0; i < people.length; i++) {
    if (candidates.contains(people[i])) {
      return people[i];
    }
  }
  return "";
}

Extract Superclass

You have two classes with common fields and methods.

Extract Class

When one class does the work of two, awkwardness results.

Consolidate Conditional Expression

You have multiple conditionals that lead to the same result or action.

例如：

double disabilityAmount() {
  if (seniority < 2) {
    return 0;
  }
  if (monthsDisabled > 12) {
    return 0;
  }
  if (isPartTime) {
    return 0;
  }
  // compute the disability amount
  //...
}

改为

double disabilityAmount() {
  if (isNotEligableForDisability()) {
    return 0;
  }
  // compute the disability amount
  //...
}

解决方案：

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Consolidate Duplicate Conditional Fragments

例如：

if (isSpecialDeal()) {
  total = price * 0.95;
  send();
}
else {
  total = price * 0.98;
  send();
}

改为

if (isSpecialDeal()) {
  total = price * 0.95;
}
else {
  total = price * 0.98;
}
send();

Lazy Class

如果一个类的几乎不会被用上，就应该被删除。

解决方案：

Inline Class

A class does almost nothing and is not responsible for anything, and no additional responsibilities are planned for it.

Collapse Hierarchy

You have a class hierarchy in which a subclass is practically the same as its superclass.

Data Class

数据类是指仅包含用于访问它们的字段和粗略方法的类（getter和setter）。这些只是其他类使用的数据的容器。这些类不包含任何其他功能，也不能独立操作它们拥有的数据。

解决方案：

Encapsulate Field

例如：

class Person {
  public String name;
}

改为

class Person {
  private String name;

  public String getName() {
    return name;
  }
  public void setName(String arg) {
    name = arg;
  }
}

Encapsulate Collection

A class contains a collection field and a simple getter and setter for working with the collection.

Move Method

A method is used more in another class than in its own class.

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Remove Setting Method

The value of a field should be set only when it is created, and not change at any time after that.

Hide Method

A method is not used by other classes or is used only inside its own class hierarchy.

Dead Code

不再被使用的变量，参数，字段，方法或类。

解决方案：

使用好的IDE，通过IDE标注找到没被使用的变量，参数，字段，方法或类。
Inline Class

A class does almost nothing and is not responsible for anything, and no additional responsibilities are planned for it.

Collapse Hierarchy

You have a class hierarchy in which a subclass is practically the same as its superclass.

Remove Parameter

A parameter is not used in the body of a method.

Couplers

类与类之间过度耦合。

Feature Envy

方法访问另一个对象的数据多于访问自己的数据。

解决方案：

Move Method

A method is used more in another class than in its own class.

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Inappropriate Intimacy

一个类使用另一个类的内部字段和方法。

解决方案：

Move Method

A method is used more in another class than in its own class.

Move Field

A field is used more in another class than in its own class.

Extract Class

When one class does the work of two, awkwardness results.

Hide Delegate

The client gets object B from a field or method of object А. Then the client calls a method of object B.

Change Bidirectional Association to Unidirectional

You have a bidirectional association between classes, but one of the classes does not use the other’s features.

Replace Delegation with Inheritance

A class contains many simple methods that delegate to all methods of another class.

Message Chains

在代码中你看到类似于这样的一系列的方法调用： $a->b()->c()->d()。

解决方案：

Hide Delegate

The client gets object B from a field or method of object А. Then the client calls a method of object B.

Extract method

例如：

void printOwing() {
  printBanner();

  //print details
  System.out.println("name: " + name);
  System.out.println("amount: " + getOutstanding());
}

改为

void printOwing() {
  printBanner();
  printDetails(getOutstanding());
}

void printDetails(double outstanding) {
  System.out.println("name: " + name);
  System.out.println("amount: " + outstanding);
}

Move Method

A method is used more in another class than in its own class.

Middle Man

如果一个类只执行将工作委托给另一个类，那么它就没有存在的必要。

解决方案：

Remove Middle Man

A class has too many methods that simply delegate to other objects.

气味代码与重构

类型一：Bloaters

Long Method

Large Class

Primitive Obsession

Long Parameter List

Data Clumps

类型二：Object-Orientation Abusers

Switch Statements

Temporary Field

Refused Bequest

Alternative Classes with Different Interfaces

类型三：Change Preventers

Divergent Change

Shotgun Surgery

Parallel Inheritance Hierarchies

类型四：Dispensables

Comments

Duplicate Code

Lazy Class

Data Class

Dead Code

Couplers

Feature Envy

Inappropriate Intimacy

Message Chains

Middle Man

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