为什么:如果未被ActiveRecord验证识别?

我有一个问题,在ActiveRecord验证中的:if子句没有得到遵守。

我的模型有一个IP端口属性,我正在验证该属性是否存在,是否为数字,是否在某个范围内。我试图确保每个条件只生成一个错误。我不希望出现这样的情况:一个空属性导致向用户显示三条消息,说明它不存在、必需且不是数字。

这是我的模型

class Arc < ActiveRecord::Base
  attr_accessible :ip_port

  validates_presence_of :ip_port
  validates_numericality_of :ip_port, :allow_blank => true
  validates_inclusion_of :ip_port, :in => 1025..65535, :allow_blank => true, 
     :if => Proc.new {|arc| arc.ip_port.to_s.match(/^\d+$/) }
end

这是我的模型规范及其结果。

describe Arc do
  it "should be valid with valid attributes" do
    Arc.new(:ip_port => 1200).should be_valid
  end
  it "should be invalid with a non-numberic port" do
    Arc.new(:ip_port => "test").should be_invalid
  end
  it "should be invalid with a missing port" do
    Arc.new(:ip_port => nil).should be_invalid
  end
  it "should have one error with a missing port" do
    a = Arc.new(:ip_port => nil)
    a.should be_invalid
    a.should have(1).errors_on(:ip_port)
  end
  it "should have one error with a non-numeric port" do
    a = Arc.new(:ip_port => "test")
    a.should be_invalid
    a.should have(1).errors_on(:ip_port)
  end
  it "should have one error with a numeric port outside the range" do
    a = Arc.new(:ip_port => 999)
    a.should be_invalid
    a.should have(1).errors_on(:ip_port)
  end
end

Arc
- should be valid with valid attributes
- should be invalid with a non-numberic port
- should be invalid with a missing port
- should have one error with a missing port
- should have one error with a non-numeric port (FAILED - 1)
- should have one error with a numeric port outside the range

1)
'Arc should have one error with a non-numeric port' FAILED
expected 1 errors on :ip_port, got 2
./spec/models/arc_spec.rb:21:

Finished in 0.108245 seconds

我的问题是,当:if子句阻止validates-include被调用时,为什么非数字IP端口会出现两个错误。

这是在OS/X 10.6.3上带有Ruby1.8.7的Rails 2.3.5。