所以我创建了一个params哈希，为它赋值，试图提取一个值。

person1 = Person.new
person1.first = "Tim"
person1.last = "Happy"

person2 = Person.new
person2.first = "Zack"
person2.last = "Sad"

person3 = Person.new
person3.first = "Al"
person3.last = "Angry"

params = {:father => person1, :mother => person2, :child => person3} #params hash
puts params[:father][:first]
person1 = Person.new
person1.first = "Tim"
pers