以此示例Proc：
proc = Proc.new {|x,y,&block| block.call(x,self.instance_method)}
它有两个参数x和y,也是一个块.
我想使用不同的值来执行该块.这样的东西几乎可以工作：
some_object.instance_exec("x arg","y arg",&proc)
但是,这不允许你传递一个块.这也不行
some_object.instance_exec("x arg",another_proc,&proc)
也没有
some_object.instance_exec("x arg",&another_proc,&proc)
我不知道还有什么可以在这里工作.这是可能的,如果是这样做的话呢？
编辑：基本上如果您可以通过更改change_scope_of_proc方法来获取此rspec文件,您已经解决了我的问题.
require 'rspec'
class SomeClass
def instance_method(x)
"Hello #{x}"
end
end
class AnotherClass
def instance_method(x)
"Goodbye #{x}"
end
def make_proc
Proc.new do |x,&block|
instance_method(block.call(x))
end
end
end
def change_scope_of_proc(new_self,proc)
# TODO fix me!!!
proc
end
describe "change_scope_of_proc" do
it "should change the instance method that is called" do
some_class = SomeClass.new
another_class = AnotherClass.new
proc = another_class.make_proc
fixed_proc = change_scope_of_proc(some_class,proc)
result = fixed_proc.call("Wor") do |x|
"#{x}ld"
end
result.should == "Hello World"
end
end
解决方法
要解决这个问题,您需要将Proc重新绑定到新类.
这是您的解决方案,利用Rails core_ext中的一些好的代码：
require 'rspec'
# Same as original post
class SomeClass
def instance_method(x)
"Hello #{x}"
end
end
# Same as original post
class AnotherClass
def instance_method(x)
"Goodbye #{x}"
end
def make_proc
Proc.new do |x,&block|
instance_method(block.call(x))
end
end
end
### SOLUTION ###
# From activesupport lib/active_support/core_ext/kernel/singleton_class.rb
module Kernel
# Returns the object's singleton class.
def singleton_class
class << self
self
end
end unless respond_to?(:singleton_class) # exists in 1.9.2
# class_eval on an object acts like singleton_class.class_eval.
def class_eval(*args,&block)
singleton_class.class_eval(*args,&block)
end
end
# From activesupport lib/active_support/core_ext/proc.rb
class Proc #:nodoc:
def bind(object)
block,time = self,Time.now
object.class_eval do
method_name = "__bind_#{time.to_i}_#{time.usec}"
define_method(method_name,&block)
method = instance_method(method_name)
remove_method(method_name)
method
end.bind(object)
end
end
# Here's the method you requested
def change_scope_of_proc(new_self,proc)
return proc.bind(new_self)
end
# Same as original post
describe "change_scope_of_proc" do
it "should change the instance method that is called" do
some_class = SomeClass.new
another_class = AnotherClass.new
proc = another_class.make_proc
fixed_proc = change_scope_of_proc(some_class,proc)
result = fixed_proc.call("Wor") do |x|
"#{x}ld"
end
result.should == "Hello World"
end
end