ruby - Unexpected output in string format with instance variables -
i writing console application , want display prompt command number (i.e variable increased every time user presses enter).
expected output:
[0] app_name > 1 [1] app_name > 2 [2] app_name > here code:
class prompt attr_accessor :format, :string, :prompt, :index def initialize init_vars @format = "[%s] %s > " @string = [@index, "app_name"] @prompt = @format % @string end def init_vars @index = 0 end def update_prompt @index += 1 @prompt = @format % @string end end require 'readline' prompt = prompt.new while last = readline.readline(prompt.prompt) prompt.update_prompt puts prompt.index end output:
[0] app_name > 1 [0] app_name > 2 [0] app_name > when change line:
@prompt = @format % @string to:
@prompt = @format % [@index, "app_name"] i plan use internal framework, , user specify @format , @string , produce prompt. believe changing line above not work.
may explain doing wrong?
here working code:
class prompt attr_accessor :format, :string, :prompt, :index def initialize @index = -1 @format = "[%d] %s > " update_prompt end def update_prompt @index += 1 @string = @index, "app_name" @prompt = @format % @string end end require 'readline' prompt = prompt.new while last = readline.readline(prompt.prompt) prompt.update_prompt #de puts prompt.index end output expected:
[0] app_name > [1] app_name > [2] app_name > [3] app_name > [4] app_name > [5] app_name > [6] app_name > the @string being frozen @ @index == 0 needed updated, @index was. thought @index update, , reference being stored in @string, value being stored... not reference updated. i'm curious why, i've fixed code regardless.
knowing know how @string handled...
here smaller version:
class prompt attr_accessor :format, :string, :prompt, :index def initialize @index = -1 @format = "[%d] %s > " update_prompt end def update_prompt @prompt = @format % [ @index += 1, "app_name" ] end end
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