Fix cache read twice for a single value

[qichunren]

No description provided.

[huacnlee]

It looks like no different?

[qichunren]

class Hello

  def name
    puts "Try name"
    "Jim"
  end

  def call
    if name.nil?
      puts "name is nil"
    end
    puts "Name: #{name}"
  end

  def call_improve
    stored_value = name
    if stored_value.nil?
      puts "name is nil"
    end
    puts "Name: #{stored_value}"
  end
end

hello = Hello.new
puts "\nTest call"
hello.call
puts "\nTest call_improve"
hello.call_improve

Out put result:

Test call
Try name
Try name
Name: Jim

Test call_improve
Try name
Name: Jim

[huacnlee]

Close #255