为什么我们不能在救援中访问局部变量？

Question

局部变量

begin
  transaction  #Code inside transaction 
    object = Class.new attributes
    raise unless object.save!
  end 
rescue
  puts object.error.full_messages # Why can't we use local varible inside rescue ?
end

实例变量

begin
  transaction  #Code inside transaction 
    @object = Class.new attributes
    raise unless @object.save!
  end 
rescue
  puts @object.error.full_messages # This is working fine.
end

Answer 1

你当然可以begin在相应的rescue块中访问a 中定义的局部变量(当然,假设在设置变量之后引发了异常).

您不能做的是访问块外部块内定义的局部变量.这与例外无关.看这个简单的例子:

define transaction() yield end
transaction do
  x = 42
end
puts x # This will cause an error because `x` is not defined here.

你可以做些什么来解决这个问题,就是在块之前定义变量(你可以将它设置为nil),然后在块中设置它.

x = nil
transaction do
  x = 42
end
puts x # Will print 42

因此,如果您更改此代码,它将起作用:

begin
  object = nil
  transaction do  #Code inside transaction 
    object = Class.new attributes
    raise unless object.save!
  end 
rescue
  puts object.error.full_messages # Why can't we use local varible inside rescue ?
end