Rails 3 - 自定义验证程序

Question

我试图在我的应用程序上使自定义验证程序工作。

我已经配置好我的config.autoload.paths，它加载正常。

问题出在验证器本身。

结果的

binding pry

instance variables: @attributes @options @with 
locals: _ _dir_ _ex_ _file_ _in_ _out_ _pry_ attribute record value 
[12] pry(#<FileCountValidator>)> value 
=> [#<Attachment id: 60, description: nil, file: "cache_600_1__img_948867_5770137d84a6c79ac825886938e...", attachable_type: "Post", attachable_id: 15, created_at: "2012-03-10 14:50:54", updated_at: "2012-03-10 14:50:54">, 
#<Attachment id: 61, description: nil, file: "cache_600_1__img_948867_90f64e01b9c871ec656a884e015...", attachable_type: "Post", attachable_id: 15, created_at: "2012-03-10 14:50:54", updated_at: "2012-03-10 14:50:54">, 
#<Attachment id: 62, description: nil, file: "cache_600_1__img_948867_85eda3946c27fa90566403ac941...", attachable_type: "Post", attachable_id: 15, created_at: "2012-03-10 14:50:54", updated_at: "2012-03-10 14:50:54">, 
#<Attachment id: nil, description: nil, file: nil, attachable_type: "Post", attachable_id: 15, created_at: nil, updated_at: nil>] 
[13] pry(#<FileCountValidator>)> value > @with 
TypeError: compared with non class/module 
from /home/kleber/.rvm/gems/ruby-1.9.3-p125/gems/activerecord-3.2.1/lib/active_record/relation/delegation.rb:20:in `>' 
[14] pry(#<FileCountValidator>)> value.size > @with 
=> true 
[15] pry(#<FileCountValidator>)> value.size 
=> 4 
[16] pry(#<FileCountValidator>)> @with 
=> 3 
[17] pry(#<FileCountValidator>)> 

所以，我试图让这个comparisson正是像我一样的撬调试控制台上。

def validate_each(record, attribute, value) 
    #binding.pry 
    record.errors.add(attribute,"#{@with} attachments per post only. #{attribute['file'].size} detected.") if value.size > @with 
    end 

但这样做，返回我的错误：

NoMethodError (undefined method `size' for nil:NilClass): 
    lib/validators/file_count_validator.rb:11:in `validate_each' 
    app/controllers/posts_controller.rb:61:in `block in update' 
    app/controllers/posts_controller.rb:60:in `update' 

还有什么办法赶value它获得进入validate_each方法之前？

Answer 1

对不起，但通过的值似乎是正确的。 value意味着该记录的那个属性的值，即record.send(attribute)应该等于该值。

调用validates :attachments, :photo_count => 2不会发送2到validate_each方法作为参数value。你可以做:photo_count => true，这是我通常做的，甚至是:photo_count => "foo"。您的validates声明中的photo_count用于规定验证程序将通过传递嵌入选项哈希中的值（即，用于陈述示例的2或true或“foo”）来调用。

这里有一个方法没有通过验证器的限制。

创建一个Constants类并定义MAX_ATTACHMENTS常量。我通常在models/constants.rb。

class Constants 
    MAX_ATTACHMENTS = 1 
end 

然后，在验证，你可以做

class PhotoCountValidator < ActiveModel::EachValidator 
    def validate_each(record, attribute, value) 
    record.errors.add(attribute,"#{Constants::MAX_ATTACHMENTS} attachments per post only.") if record.send(attribute).size > Constants::MAX_ATTACHMENTS 
    end 
end 

是传递参数的验证另一种方式：

validates :attachments, :photo_count => 3 #desired_limit 

占优PhotoCountValidator类初始化方法，并初始化一个类变量：

def initialize(options) 
    @@max_objects = options[:with] # the options hash will be as {:attributes=>[:attachments], :with=>3}, where :with contains the desired limit passed 
    super 
end 

然后validate_each方法中：

record.errors.add(attribute,"#{@@max_objects} attachments per post only.") if record.send(attribute).size > @@max_objects