更换Ruby中的to_s方法。不打印所需的字符串 [英] Replacing the to_s method in Ruby. Not printing out desired string

问题描述

所以，我刚刚开始学习Ruby，我在我的类中包含了一个to_s方法，这样我可以简单地将对象传递给一个puts方法，并返回不仅仅是Object ID。我犯了一个错误并将其定义为：

  def to_s 
输入I'm＃{@ name}健康度为＃{@ health}。 
 end 
  

而不是：

  def to_s 
我是＃{@ name}，运行状况为＃{@ health}。 
 end 
  

所以，当我使用第一个代码块时：

  player1 = Player.new（larry）
 put player1 
  pre> 
 
 
当我执行上面两行代码而不只是字符串时，我得到一个对象ID和一个字符串。为什么是这样？我得到这个输出：
 我是Larry，健康状态为90. 
＃< Player：0x007fca1c08​​b270> 
  
我想想为什么第一个版本的程序不只是打印出字符串到控制台，而是返回对象ID和字符串。我想，当我把对象传递给puts，所有发生的是，puts转向，并调用to_s方法来获取玩家的字符串表示。当给定的参数不是字符串或数组时 
 
解决方案
调用 rb_obj_as_string 将其参数转换为字符串（参见 http://rxr.whitequark.org 对此有用），您可以看到它定义为
  VALUE rb_obj_as_string（VALUE obj） 
 {
 VALUE str 
 
 if（RB_TYPE_P（obj，T_STRING））{
 return obj; 
} 
 str = rb_funcall（obj，id_to_s，0）; 
 if（！RB_TYPE_P（str，T_STRING））
 return rb_any_to_s（obj）; 
 if（OBJ_TAINTED（obj））OBJ_TAINT（str）; 
 return str; 
} 
  
简要说明：
 
 
 
 
 
如果参数已经是字符串，则直接返回
 
 
调用 to_s  
 
 
如果结果不是字符串，调用 rb_any_to_s 并返回。
 
 
 
 
 
  rb_any_to_s 是什么实现你看到的默认类名和id结果：对于任何对象，它返回一个形式的字符串＃ 
 
 
返回到您的代码，当您运行 puts player1 它会调用 rb_obj_as_string 将您的播放器转换为字符串。
 
 
 
 code> to_s 方法，它使用 puts 输出消息。你的方法然后返回nil（因为这是放总是返回）所以ruby调用 rb_any_to_s   puts 结束使用。 
 
So, I am just beginning to learn Ruby and I included a to_s method in my Class so that I can simply pass the Object to a puts method and have it return more than just the Object ID. I made a mistake and defined it as such:
def to_s
    puts "I'm #{@name} with a health of #{@health}."
end
instead of:
def to_s
    "I'm #{@name} with a health of #{@health}."
end
So, when I do this while using the first code block:
player1 = Player.new("larry")
puts player1
I get an object ID and a string when I execute the above two lines of code and not just the string. Why is this? I get this output:
I'm Larry with a health of 90.
#<Player:0x007fca1c08b270>
I am trying to think about why the first version of the program doesn't just print out the string to console, but instead returns the object ID and the string. I thought that when I pass the object to puts, all that is happening is that puts turns around and calls the to_s method to get the player's string representation. Right?
解决方案
When given arguments that are not strings or arrays puts calls rb_obj_as_string to turn its arguments into strings (see rb_io_puts)

If you search for rb_obj_as_string through the ruby codebase (I find http://rxr.whitequark.org useful for this) you can see it's defined as
VALUE rb_obj_as_string(VALUE obj)
{
  VALUE str;

  if (RB_TYPE_P(obj, T_STRING)) {
    return obj;
  }
  str = rb_funcall(obj, id_to_s, 0);
  if (!RB_TYPE_P(str, T_STRING))
    return rb_any_to_s(obj);
  if (OBJ_TAINTED(obj)) OBJ_TAINT(str);
  return str;
}
In brief this:


returns straightaway if the argument is already a string
calls to_s
if the result is not a string, call rb_any_to_s and return that.


rb_any_to_s is what implements the default "class name and id" result that you're seeing: for any object it returns a string of the form #<ClassName: 0x1234567890abcdef>

Returning to your code, when you run puts player1 it calls  rb_obj_as_string to convert your player to a string.

This first calls your to_s method, which uses puts to output your message. Your method then returns nil (because that's what puts always returns) so ruby calls rb_any_to_s, and that is what the outermost puts ends up using. 

                        
这篇关于更换Ruby中的to_s方法。不打印所需的字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！