未评估类方法 NoMethodError

Question

我不明白为什么在尝试调用类方法“addStudent”时会收到 NoMethodError。 我添加了 self 以从实例更改为类方法，并且我三重检查了我的语法以确保我引用了正确的对象。

我在 school 对象和方法上运行了一个简单的 put，它们都引用了 School 类的同一个实例。这是代码。

class School
   attr_accessor :name, :location, :instructors, :students
   attr_reader :ranking
   @@SCHOOLS = []


    def initialize(name, location, ranking, students, instructors)
       @name = name
       @location = location
       @ranking = ranking
       @students = students
       @instructors = instructors
       @@SCHOOLS << self
    end

    def self.setRanking= (ranking)
       @ranking = ranking
    end

    def self.addStudent= (name, grade, semester)
       @students << {:name => name, :grade => grade, :semester => semester}
    end


    def self.removeStudent(name)
         @students.delete_if { |student_hash| student_hash[:name] == name }
    end
end

 school = School.new ("Happy Funtime School", 
"NYC", 
1, 
[   {:name => "Marissa", :grade => "B"},
    {:name=>"Billy", :grade => "F"},
    {:name => "Frank", :grade => "A"},
    {:name => "Sophie", :grade => "C"}  ],
[ 
    {:name=>"Blake", :subject=>"being awesome" },
    {:name=>"Ashley", :subject=>"being better than blake"},
    {:name=>"Jeff", :subject=>"karaoke"}
                                        ]    

)

school.addStudent("Jesus", "Z", "Y")

错误：

 rb:114:in `<main>': undefined method `addStudent' for #<School:0x007fca64099ff8> (NoMethodError)

Answer 1

1. 您将setRanking、addStudent、removeStudent 方法设为类方法，方法是在它们前面加上self.。但是您使用方法addStudent 作为实例方法。移除self.，使其成为实例方法。

2. 您正在调用addStduent，但将其定义为addStudent=（尾随=）。

---

def setRanking(ranking)
  @ranking = ranking
end

def addStudent(name, grade, semester)
  @students << {:name => name, :grade => grade, :semester => semester}
end


def removeStudent(name)
  @students.delete_if { |student_hash| student_hash[:name] == name }
end