使用带参数的instance_eval调用proc？

I know this works:

我知道这有效：

proc = Proc.new do
  puts self.hi + ' world'
end

class Usa
  def hi
    "Hello!"
  end
end
Usa.new.instance_eval &proc

However I want to pass arguments to proc, so I tried this which does not work:

但是我想将参数传递给proc，所以我试过这个不起作用：

proc = Proc.new do |greeting| 
  puts self.hi + greeting
end

class Usa
  def hi
    "Hello!"
  end
end
Usa.new.instance_eval &proc, 'world' # does not work
Usa.new.instance_eval &proc('world') # does not work

Can anyone help me make it work?

任何人都可以帮助我使它工作吗？

1 个解决方案

#1

Use instance_exec instead of instance_eval when you need to pass arguments.

需要传递参数时，请使用instance_exec而不是instance_eval。

proc = Proc.new do |greeting| 
  puts self.hi + greeting
end

class Usa
  def hi
    "Hello, "
  end
end
Usa.new.instance_exec 'world!', &proc # => "Hello, world!"

Note: it's new to Ruby 1.8.7, so upgrade or require 'backports' if needed.

注意：它是Ruby 1.8.7的新功能，因此如果需要，升级或需要“backports”。

#1