28 Feb 2014
ruby on rails .nil?, .empty?, .blank?, .present?区别
- 区别
.nil? 和 .empty? 是ruby的方法。.blank? 是rails的方法.
.nil? 判断对象是否存在(nil),不存在的对象都是nil.
.empty? 对象已经存在,判断是否为空,比如一个字符串是否为空串,或者一个数组中是否有值.
.blank? 相当于同时满足 .nil? 和 .empty? 。railsAPI中的解释是如果对象是: false, empty, 空白字符. 比如说: "", " ", nil , [], 和{}都算是blank.(object.blank? 相当于 object.nil? || object.empty?).
.present? 方法就是blank?方法的相反,判断是否存在,因此present?方法与!blank?方法两者表达的意思是一样的.
- 示例
.nil?
nil.nil? => true false.nil? => false 1.nil? => false 0.nil? => false "".nil? => false [].nil? => false
.empty?
"".empty? => true "abc".empty? => false [].empty? => true [1, 2, 3].empty? => false 1.empty? => NoMethodError #说明 empty? 方法不能用于整数
.blank?
true.blank? =>false false.blank? =>true "true".blank? =>false "".blank? =>true "\n".blank? =>true '\n'.blank? =>false 'true'.blank? =>false ''.blank? =>true 1.blank? =>false [].blank? =>true [1].blank? =>false
Til next time,
Bohsu.
at 17:27