在Ruby中定义method_missing
方法有什么需要注意的地方吗?我想知道是否存在一些不太明显的来自继承、异常抛出、性能或其他任何方面的交互。
最佳答案
一个有点明显的:总是重新定义 respond_to?
如果你重新定义 method_missing
。如果 method_missing(:sym)
有效,respond_to?(:sym)
应该总是返回 true。许多图书馆都依赖于此。
稍后:
一个例子:
# Wrap a Foo; don't expose the internal guts.
# Pass any method that starts with 'a' on to the
# Foo.
class FooWrapper
def initialize(foo)
@foo = foo
end
def some_method_that_doesnt_start_with_a
'bar'
end
def a_method_that_does_start_with_a
'baz'
end
def respond_to?(sym, include_private = false)
pass_sym_to_foo?(sym) || super(sym, include_private)
end
def method_missing(sym, *args, &block)
return foo.call(sym, *args, &block) if pass_sym_to_foo?(sym)
super(sym, *args, &block)
end
private
def pass_sym_to_foo?(sym)
sym.to_s =~ /^a/ && @foo.respond_to?(sym)
end
end
class Foo
def argh
'argh'
end
def blech
'blech'
end
end
w = FooWrapper.new(Foo.new)
w.respond_to?(:some_method_that_doesnt_start_with_a)
# => true
w.some_method_that_doesnt_start_with_a
# => 'bar'
w.respond_to?(:a_method_that_does_start_with_a)
# => true
w.a_method_that_does_start_with_a
# => 'baz'
w.respond_to?(:argh)
# => true
w.argh
# => 'argh'
w.respond_to?(:blech)
# => false
w.blech
# NoMethodError
w.respond_to?(:glem!)
# => false
w.glem!
# NoMethodError
w.respond_to?(:apples?)
w.apples?
# NoMethodError
关于ruby - Ruby 中的 method_missing 陷阱,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/291132/