首先是不为空validates :name,presence:{message:'blank is not allowed'}
唯一性：validates :name,uniqueness:{message:'already exist!',case_sensitive: false}#case_sensitive区分大小写
长度：validates :name,length:{in: 6..20,message:'must in 6-20 byte'}
格式：validates :name,format:{with: /[a-z]/,message:'must contain at least one lower case character'}
范围：validates :country,inclusion:{in:['China','USA','Jpan','Mexico'],message:'must one of China USA Jpan Mexico '}
数字：validates :graduate,numericality:{allow_nil: true,greater_than: 1920,less_than_or_equal_to:Time.now.year}
validates :description,presence:true,if: :require_description_presence?
def require_description_presence?
self.can_send_mail
end
这个validates :description,presence: true只有在require_description_presence?方法返回true的时候才会起作用
validate :description_length_words
def description_length_words
unless self.description.blank? then
num_words = self.description.split.length
if num_words < 5 then
self.errors.add(:description,'must be at least 5 words long')
elsif num_words > 50
self.errors.add(:description,'must be at most 50 words long')
end
end
end