ruby - 检测递归调用

Question

检测递归方法调用的最佳方法是什么？或许，可以做成这样的格式：

def foo
  if some_code_to_detect_recursive_call
    ...
  else
    ...
  end
end

我可以想到一种解析caller信息的方法，但我有兴趣看看是否有更好的方法。

Answer 1

只需在进入您的方法后增加一个计数器（实例或全局变量）并在退出时减少它。

在入口处，计数器会告诉您您的递归级别。

Answer 2

def is_recursive(max_recursive_calls=2)
  calls = caller.inject(0) do |calls, line|
    break calls if calls >= max_recursive_calls
    calls += 1 if line == caller[-2]
    calls
  end
  calls >= max_recursive_calls
end

测试用例：

# 1
def recursive
  p "case #1"
  recursive unless is_recursive
end

# 2
def recursive_a
  p "case #2.1"
  recursive_b unless is_recursive
end

def recursive_b
  p "case #2.2"
  recursive_a unless is_recursive
end

# 3
def recursive_cond(iter=0, limit=10)
  p "case #3"
  recursive_cond(iter + 1, limit) unless iter > limit || is_recursive(50)
end

recursive
recursive_a
recursive_b
recursive_cond

p "If you see this: is_recursive function implemented correctly"

输出

"case #1"
"case #1"
"case #2.1"
"case #2.2"
"case #2.1"
"case #2.2"
"case #2.1"
"case #2.2"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"case #3"
"If you see this: is_recursive function implemented correctly"