Ruby 中的各种变量(local/instance/class/global variable and assignment method)

# local variable
10.times{ |i| print("=")}
puts("local variable")
1.times do
a = 1
b = "a"
puts "local variables in the block: #{local_variables.join ", "}"
end

puts "no local variables outside the block" if local_variables.empty?

# instance variable
10.times{ |i| print("=")}
puts("instance variable")
class C
def initialize(value)
@instance_variable = value
end

def value
@instance_variable
end
end

object1 = C.new "some value"
object2 = C.new "other value"

p object1.value # prints "some value"
p object2.value # prints "other value"

#class variable
10.times{ |i| print("=")}
puts("class variable")
class A
@@class_variable = 0

def value
@@class_variable
end

def update
@@class_variable = @@class_variable + 1
end
end

class B < A
def update
@@class_variable = @@class_variable + 2
end
end

a = A.new
b = B.new

puts "A value: #{a.value}" #0
puts "B value: #{b.value}" #0

puts "update A"
a.update

puts "A value: #{a.value}"
puts "B value: #{b.value}"

puts "update B"
b.update

puts "A value: #{a.value}"
puts "B value: #{b.value}"

puts "update A"
a.update

puts "A value: #{a.value}"
puts "B value: #{b.value}"

#global variable
10.times{ |i| print("=")}
puts("global variable")
$global = 0

class E
puts "in a class: #{$global}"

def my_method
puts "in a method: #{$global}"

$global = $global + 1
$other_global = 3
end
end

E.new.my_method

puts "at top-level, $global: #{$global}, $other_global: #{$other_global}"

# Assignment method
10.times{ |i| print("=")}
puts("Assignment method")
class F
@value
attr_accessor :value

def my_method
#self.value = 42
@value = 42;
puts "local_variables: #{local_variables.join ", "}"
puts "@value: #{@value.inspect}"
end
end

F.new.my_method