使用策略模式將基於類型或狀態(tài)的複雜條件邏輯替換為可擴(kuò)展的策略類；2. 通過(guò)多態(tài)消除類型檢查，讓每個(gè)對(duì)象自行實(shí)現(xiàn)其行為；3. 用查找表（如字典）替代簡(jiǎn)單的值到值或值到動(dòng)作的映射；4. 使用守衛(wèi)子句提前返回，減少嵌套層次；5. 提取方法以命名和隔離條件邏輯。這些重構(gòu)方法將復(fù)雜的條件語(yǔ)句轉(zhuǎn)化為清晰、可維護(hù)的代碼，提升可讀性和可擴(kuò)展性，且完全遵循開(kāi)閉原則，最終實(shí)現(xiàn)乾淨(jìng)、表達(dá)力強(qiáng)的設(shè)計(jì)。

Complex conditionals—often called “God Switches”—are a common code smell that make software harder to read, test, and maintain. These sprawling if-else or switch statements, usually driven by multiple conditions or types, tend to grow over time, becoming a breeding ground for bugs and technical debt. Refactoring them is essential for writing clean, maintainable code.

The goal isn't to eliminate conditionals entirely—they're a necessary part of programming—but to manage their complexity by extracting logic, reducing duplication, and aligning code with object-oriented or functional design principles.

Here's how to refactor God Switches into clean, expressive code.

Replace Conditional with Strategy Pattern

When a switch or if-else block chooses behavior based on type or status, the Strategy Pattern is a powerful alternative.

Example:

 # Before: God Switch
def calculate_bonus(employee_type, sales):
    if employee_type == "manager":
        return sales * 0.2
    elif employee_type == "salesperson":
        return sales * 0.1
    elif employee_type == "intern":
        return 0
    else:
        raise ValueError("Unknown employee type")

This function will grow with every new role and is hard to test and extend.

Refactor:

 from abc import ABC, abstractmethod

class BonusStrategy(ABC):
    @abstractmethod
    def calculate(self, sales):
        pass

class ManagerBonus(BonusStrategy):
    def calculate(self, sales):
        return sales * 0.2

class SalespersonBonus(BonusStrategy):
    def calculate(self, sales):
        return sales * 0.1

class InternBonus(BonusStrategy):
    def calculate(self, sales):
        return 0

# Map types to strategies
STRATEGIES = {
    "manager": ManagerBonus(),
    "salesperson": SalespersonBonus(),
    "intern": InternBonus(),
}

def calculate_bonus(employee_type, sales):
    strategy = STRATEGIES.get(employee_type)
    if not strategy:
        raise ValueError("Unknown employee type")
    return strategy.calculate(sales)

Now adding a new role means adding a new class and updating the map—no touching existing logic. Open/Closed Principle achieved.

Use Polymorphism to Eliminate Type Checks

If you're switching on object type, it's a sign you should be using inheritance and polymorphism.

Example:

 # Before
def pay_employee(employee):
    if employee.type == "full_time":
        return f"Paid monthly: {employee.salary}"
    elif employee.type == "contractor":
        return f"Paid hourly: {employee.hourly_rate * 160}"

Refactor:

 class Employee(ABC):
    @abstractmethod
    def pay(self):
        pass

class FullTimeEmployee(Employee):
    def pay(self):
        return f"Paid monthly: {self.salary}"

class Contractor(Employee):
    def pay(self):
        return f"Paid hourly: {self.hourly_rate * 160}"

# Now usage is uniform
def pay_employee(employee: Employee):
    return employee.pay()

The conditional is gone. Each type knows how to pay itself. This makes the code extensible and easier to reason about.

Replace Conditional Logic with Lookup Tables

For simple mappings—like status codes to messages or actions—use a dictionary or map instead of if/elif chains.

Example:

 # Before
def get_status_message(status):
    if status == "pending":
        return "Your order is pending"
    elif status == "shipped":
        return "Your order has shipped"
    elif status == "delivered":
        return "Your order was delivered"
    else:
        return "Unknown status"

Refactor:

 STATUS_MESSAGES = {
    "pending": "Your order is pending",
    "shipped": "Your order has shipped",
    "delivered": "Your order was delivered",
}

def get_status_message(status):
    return STATUS_MESSAGES.get(status, "Unknown status")

Clean, fast, and data-driven. No logic, just lookup.

You can even map to functions:

 ACTIONS = {
    "save": save_document,
    "load": load_document,
    "delete": delete_document,
}

def handle_action(action):
    func = ACTIONS.get(action)
    if func:
        func()
    else:
        raise ValueError(f"Unknown action: {action}")

Guard Clauses: Simplify Early Returns

Sometimes the issue isn't the switch itself, but nested conditionals. Use guard clauses to return early and flatten the logic.

Example:

 # Before
def process_user(user):
    if user is not None:
        if user.is_active:
            if user.has_permission:
                return "Processing..."
            else:
                return "No permission"
        else:
            return "Inactive user"
    else:
        return "No user provided"

Refactor:

 def process_user(user):
    if user is None:
        return "No user provided"
    if not user.is_active:
        return "Inactive user"
    if not user.has_permission:
        return "No permission"
    return "Processing..."

Each condition is handled at the top level. The happy path flows naturally without nesting.

Summary of Refactoring Tactics

• Use Strategy Pattern when behavior varies by type or rule.
• Apply Polymorphism when conditionals check object types.
• Replace with lookup tables for simple value-to-value or value-to-action mappings.
• Extract methods to isolate conditional logic and give it a name.
• Use guard clauses to reduce nesting and improve readability.

The key insight: conditionals aren't bad—they become problematic when they're repeated, deeply nested, or tied to growing business rules. By replacing them with well-named abstractions, you turn messy logic into maintainable design.

Basically, if your conditional is growing like a weed, it's time to refactor.

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