在Rails和ruby中访问实例变量

Question

I am new to ruby and rails and sometimes I still get confused between these two. I have tried to call an instance variable by adding a name of the instance variable after an object(john.name), and I hope that the result would be John. Unfortunately NoMethodError appears. So I searched for an answer and found out that you can use instance_variable_get method to do this. However, I believe that it is possible to do this in RAILS when you want to access the instance variable of an object in VIEWS.

class Person
    def initialize(name)
        @name = name
    end
end
john = Person.new("John")
puts john.instance_variable_get(:@name)
=> John
puts john.name
=> NoMethodError

Answer 1

Use attr_reader to read the value of an instance variable

class Person
  attr_reader :name

  def initialize(name)
    @name = name
  end
end

john = Person.new("John")
john.name #=> "John"

attr_reader adds a getter method to the class, in this case

def name
  @name
end

Hope that helps!

Answer 2

You need to define the method to access your instance variable.

class Person
  def initialize(name)
    @name = name
  end

  def name
    @name
  end
end

Or you can simply add attr_accessor which will set getter and setter methods

class Person
  attr_accessor :name

  def initialize(name)
    @name = name
  end
end