這份簡明指南將 Python 程式碼氣味對應到對應的設計模式解決方案。
<code class="language-python">class CodeSmellSolutions:
DUPLICATED_CODE = [
"form_template_method",
"introduce_polymorphic_creation_with_factory_method",
"chain_constructors",
"replace_one__many_distinctions_with_composite",
"extract_composite",
"unify_interfaces_with_adapter",
"introduce_null_object",
]
LONG_METHOD = [
"compose_method",
"move_accumulation_to_collecting_parameter",
"replace_conditional_dispatcher_with_command",
"move_accumulation_to_visitor",
"replace_conditional_logic_with_strategy",
]
CONDITIONAL_COMPLEXITY = [ # Complex conditional logic
"replace_conditional_logic_with_strategy",
"move_emblishment_to_decorator",
"replace_state_altering_conditionals_with_state",
"introduce_null_object",
]
PRIMITIVE_OBSESSION = [
"replace_type_code_with_class",
"replace_state_altering_conditionals_with_state",
"replace_conditional_logic_with_strategy",
"replace_implict_tree_with_composite",
"replace_implicit_language_with_interpreter",
"move_emblishment_to_decorator",
"encapsulate_composite_with_builder",
]
INDECENT_EXPOSURE = [ # Lack of information hiding
"encapsulate_classes_with_factory"
]
SOLUTION_SPRAWL = [ # Scattered logic/responsibility
"move_creation_knowledge_to_factory"
]
ALTERNATIVE_CLASSES_WITH_DIFFERENT_INTERFACES = [ # Similar classes, different interfaces
"unify_interfaces_with_adapter"
]
LAZY_CLASS = [ # Insufficient functionality
"inline_singleton"
]
LARGE_CLASS = [
"replace_conditional_dispatcher_with_command",
"replace_state_altering_conditionals_with_state",
"replace_implict_tree_with_composite",
]
SWITCH_STATEMENTS = [ # Complex switch statements
"replace_conditional_dispatcher_with_command",
"move_accumulation_to_visitor",
]
COMBINATION_EXPLOSION = [ # Similar code for varying data
"replace_implicit_language_with_interpreter"
]
ODDBALL_SOLUTIONS = [ # Multiple solutions for same problem
"unify_interfaces_with_adapter"
]</code>Python 中的重構範例
專案將重構範例從 Refactoring to Patterns (Joshua Kerievsky) 翻譯成 Python。每個範例都顯示原始和重構的程式碼，突出顯示改進。 重構過程涉及解釋 UML 圖並使 Java 程式碼適應 Python 的細微差別（處理循環導入和介面）。
範例：撰寫方法
「Compose Method」重構透過擷取更小、更有意義的方法來簡化複雜的程式碼。
<code class="language-python"># Original (complex) code
def add(element):
readonly = False
size = 0
elements = []
if not readonly:
new_size = size + 1
if new_size > len(elements):
new_elements = []
for i in range(size):
new_elements[i] = elements[i] # Potential IndexError
elements = new_elements
size += 1
elements[size] = element # Potential IndexError
# Refactored (simplified) code
def is_at_capacity(new_size, elements):
return new_size > len(elements)
def grow_array(size, elements):
new_elements = [elements[i] for i in range(size)] # List comprehension for clarity
return new_elements
def add_element(elements, element, size):
elements.append(element) # More Pythonic approach
return len(elements) -1
def add_refactored(element):
readonly = False
if readonly:
return
size = len(elements)
new_size = size + 1
if is_at_capacity(new_size, elements):
elements = grow_array(size, elements)
size = add_element(elements, element, size)
</code>範例：多態性（測試自動化）
此範例示範了測試自動化中的多態性，抽象化了測試設定以實現可重複使用性。
<code class="language-python"># Original code (duplicate setup)
class TestCase:
pass
class DOMBuilder:
def __init__(self, orders): pass
def calc(self): return 42
class XMLBuilder:
def __init__(self, orders): pass
def calc(self): return 42
class DOMTest(TestCase):
def run_dom_test(self):
expected = 42
builder = DOMBuilder("orders")
assert builder.calc() == expected
class XMLTest(TestCase):
def run_xml_test(self):
expected = 42
builder = XMLBuilder("orders")
assert builder.calc() == expected
# Refactored code (polymorphic setup)
class OutputBuilder:
def calc(self): raise NotImplementedError
class DOMBuilderRefac(OutputBuilder):
def calc(self): return 42
class XMLBuilderRefac(OutputBuilder):
def calc(self): return 42
class TestCaseRefac:
def create_builder(self): raise NotImplementedError
def run_test(self):
expected = 42
builder = self.create_builder()
assert builder.calc() == expected
class DOMTestRefac(TestCaseRefac):
def create_builder(self): return DOMBuilderRefac()
class XMLTestRefac(TestCaseRefac):
def create_builder(self): return XMLBuilderRefac()
</code>範例：訪客模式
訪客模式將類別與其方法解耦。
<code class="language-python"># Original code (conditional logic in TextExtractor)
class Node: pass
class LinkTag(Node): pass
class Tag(Node): pass
class StringNode(Node): pass
class TextExtractor:
def extract_text(self, nodes):
result = []
for node in nodes:
if isinstance(node, StringNode): result.append("string")
elif isinstance(node, LinkTag): result.append("linktag")
elif isinstance(node, Tag): result.append("tag")
else: result.append("other")
return result
# Refactored code (using Visitor)
class NodeVisitor:
def visit_link_tag(self, node): return "linktag"
def visit_tag(self, node): return "tag"
def visit_string_node(self, node): return "string"
class Node:
def accept(self, visitor): pass
class LinkTagRefac(Node):
def accept(self, visitor): return visitor.visit_link_tag(self)
class TagRefac(Node):
def accept(self, visitor): return visitor.visit_tag(self)
class StringNodeRefac(Node):
def accept(self, visitor): return visitor.visit_string_node(self)
class TextExtractorVisitor(NodeVisitor):
def extract_text(self, nodes):
result = [node.accept(self) for node in nodes]
return result
</code>結論
這種透過重構學習設計模式的實用方法可以顯著增強理解。 翻譯程式碼時遇到的挑戰鞏固了理論知識。
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