[RUBY] Consideration about classes and instances

About classes and instances

I didn't understand the scope of class fields, class methods, instance methods, and the scope of effect of instance variables, so I summarized them.

My understanding has deepened, but a new mystery has emerged.

I would appreciate it if you could tell me any suggestions or supplements.

◆ Description (explanation)
class Zoo
def self.kind(animal_name)
@animal_name = animal_name
puts @animal_name #output:Giraffe
puts animal_name #output:Giraffe
puts @name #output:Blank
puts name #output:Zoo

def self.kind_name
puts @animal_name #output:Giraffe
# puts animal_name #output:NameError

puts @animal_name #output:Blank
# puts animal_name #output:NameError

def initialize(new_animal)
@new = new_animal
puts "#{@new}Has increased." #output:新たな仲間Has increased.

def kind(name)
@name = name
puts @animal_name #output:Blank
# puts animal_name output:NameError
puts @name #output:Lion
puts name #output:Lion

puts @name #output:Blank
puts name #output:Zoo

def color(animal_color)
@color = animal_color
#puts name output:NameError
puts "#{@new}of#{@name}Is#{@color}is" #output:新たな仲間ofライオンIs黄色is
#puts name output:NameError

#Class method self.Kind execution
#Class method self.kind_Run name

animal = Zoo.new("New companion") 
#Create animal instance, execute initialize method
puts animal.kind("Lion") 
#Kind instance method execution of animal instance

puts animal.color("yellow") 
#Execute color instance method of animal instance
#↓ Out of scope
# puts @animal_name output:Blank
# puts animal_name output:NameError
# puts @name output:Blank
#puts name output:NameError

◆ Terminal output contents


New friends have been added.


The new fellow lion is yellow

◆ Conclusion

-The output contents will be the contents read in order from the top including the class part.

-Instance variables are between class methods or between instance methods. It is possible to output each other. However, since you cannot create an instance in the class method, @ Is just a pipe that connects class methods.

-Instance variables do not cause NameError even if they are placed outside the scope, It creates a blank in the output destination.

◆ New question

-Why in a class field other than an instance method (including a class method) Is the class name output when an undefined name is output?

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