Ruby 一个元编程的代码跟踪， 求大神指教其中的调用顺序， 有点摸不着头绪了
module TraceCalls
def self.included(klass)
klass.instance_methods(false).each do |existing_method|
wrap(klass, existing_method)
end
def klass.method_added(method)
puts "@@@"
puts method
puts @trace_calls_internal
puts "$$$$"
unless @trace_calls_internal
@trace_calls_internal = true
TraceCalls.wrap(self, method)
@trace_calls_internal = false
end
end
end
def self.wrap(klass, method)
puts "###{}"
puts klass
puts method
puts "*****"
klass.instance_eval do
method_object = instance_method(method)
define_method(method) do |*args, &block|
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
result
end
end
end
end
class Example
def one(arg)
puts "One called with #{arg}"
end
end
ex1 = Example.new
ex1.one("Hello")
class Example
include TraceCalls
def two(arg1, arg2)
arg1 + arg2
end
end
ex1.one("GoodBye")
puts ex1.two(4, 5)
上面的代码跟踪有点绕，不是很清楚，希望大神们帮解析一下这其中的调用，还有像这种 ruby 元编程的东西有没有什么好方法去学习？
这个代码太混乱了 要光凭借看就理解确实不容易 至于学习其实不难 无非就是了解几个方法是干什么用得，本质上和 UNIX 编程的学习是一样的。书么就是《Ruby metaprogramming》，最权威了。
@chenge wrap(klass, existing_method) 与 TraceCalls.wrap(self, method) 这两处调用 为什么会不一样，都在同一个 module 里面啊
zgm
#8
2013年04月10日
打印结果
1:
One called with Hello
2:
##
Example
one
*****
3.1:
@@@
two
$$$$
3.2:
##
Example
two
*****
3.3:
@@@
two
true
$$$$
4:
==> calling one with ["GoodBye"]
One called with GoodBye
<== one returned nil
5:
==> calling two with [4, 5]
<== two returned 9
9
分析
1.
ex1.one("Hello") => # 打印 1
2.
include TraceCalls =>
self.included(klass) =>
wrap(klass, existing_method) =>
def self.wrap(klass, method)
# 打印 2
puts "###{}"
puts klass
puts method
puts "*****"
# 结束打印 2
klass.instance_eval do
method_object = instance_method(method)
define_method(method) do |*args, &block|
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
result
end
end
end
3.
def two(arg1, arg2)
arg1 + arg2
end
=>
def klass.method_added(method)
# 打印 3.1
puts "@@@"
puts method
puts @trace_calls_internal
puts "$$$$"
# 结束打印 3.1
unless @trace_calls_internal
@trace_calls_internal = true
TraceCalls.wrap(self, method) =>(
def self.wrap(klass, method)
# 打印 3.2
puts "###{}"
puts klass
puts method
puts "*****"
# 结束打印 3.2
klass.instance_eval do
method_object = instance_method(method)
define_method(method) do |*args, &block|
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
result
end =>(
def klass.method_added(method)
# 打印 3.3
puts "@@@"
puts method
puts @trace_calls_internal
puts "$$$$"
# 结束打印 3.3
unless @trace_calls_internal
@trace_calls_internal = true
TraceCalls.wrap(self, method)
@trace_calls_internal = false
end
end
)
end
end
)
@trace_calls_internal = false
end
# 结束打印 3
end
4.
ex1.one("GoodBye") =>
define_method(method) do |*args, &block|
# 打印 4
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
# 结束打印4
result
end
5. puts ex1.two(4, 5) =>
define_method(method) do |*args, &block|
# 打印 5
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
# 结束 打印 5
esult
end
参考资料
- Module.included http://www.ruby-doc.org/core-2.0/Module.html#method-i-included
- Module.method_added http://www.ruby-doc.org/core-2.0/Module.html#method-i-method_added
- Module.instance_methods http://www.ruby-doc.org/core-2.0/Module.html#method-i-instance_methods
- BaseObject.instance_eval http://ruby-doc.org/core-2.0/BasicObject.html#method-i-instance_eval
- BaseObject.define_method http://www.ruby-doc.org/core-2.0/BasicObject.html#method-i-instance_eval
好累，感觉不会再爱了。
简单说一下，具体的自己看书
module TraceCalls
# 回调的钩子
# 在下文include这个module后，klass即为Example类
def self.included(klass)
klass.instance_methods(false).each do |existing_method|
wrap(klass, existing_method) # 对one这个实例方法进行wrap操作
end
# 由于include在two方法前，这里对two方法进行了wrap操作
def klass.method_added(method)
unless @trace_calls_internal
@trace_calls_internal = true
TraceCalls.wrap(self, method)
@trace_calls_internal = false
end
end
end
def self.wrap(klass, method)
klass.instance_eval do
method_object = instance_method(method)
# 这里重新定义了实例方法
define_method(method) do |*args, &block|
puts "==> calling #{method} with #{args.inspect}"
result = method_object.bind(self).call(*args, &block)
puts "<== #{method} returned #{result.inspect}"
result
end
end
end
end
fsword
#13
2013年04月10日