收集不必要分配给任何变量/常量的对象 [英] Collecting objects that are not necessarly assigned to any variables/constants

问题描述

未分配给任何变量/常数的对象会立即消失(在正常情况下).在下面的第三行中，字符串"foo"未被ObjectSpace.each_object(String)捕获:

Objects that are not assigned to any variable/constant disappear immediately (under normal circumstance). In the following, the string "foo" is not captured by ObjectSpace.each_object(String) in the third line:

strings = ObjectSpace.each_object(String).to_a
  "foo"
ObjectSpace.each_object(String).to_a - strings # => []

是否可以捕获不必要分配给任何变量/常量或部分变量/常量的对象?我对捕获字符串特别感兴趣.相关域可以是文件或块.我期望如下所示:

Is it possible to capture objects that are not necessarly assigned to any variables/constants or part of any variables/constants? I am particularly interested in capturing strings. The relevant domain can be a file, or a block. I expect something like the following:

capture_all_strings do
  ...
  "a"
  s = "b"
  @s = "c"
  @@s = "d"
  S = "e"
  %q{f}
  ...
end
# => ["a", "b", "c", "d", "e", "f"]

推荐答案

Ruby在解析文件时会创建字符串实例.这是一个示例:字符串

Ruby creates the string instances when parsing your file. Here's an example: the string

"aaa #{123} zzz"

解析为:

$ ruby --dump=parsetree -e '"aaa #{123} zzz"'
###########################################################
## Do NOT use this node dump for any purpose other than  ##
## debug and research.  Compatibility is not guaranteed. ##
###########################################################

# @ NODE_SCOPE (line: 1)
# +- nd_tbl: (empty)
# +- nd_args:
# |   (null node)
# +- nd_body:
#     @ NODE_DSTR (line: 1)
#     +- nd_lit: "aaa "
#     +- nd_next->nd_head:
#     |   @ NODE_EVSTR (line: 1)
#     |   +- nd_body:
#     |       @ NODE_LIT (line: 1)
#     |       +- nd_lit: 123
#     +- nd_next->nd_next:
#         @ NODE_ARRAY (line: 1)
#         +- nd_alen: 1
#         +- nd_head:
#         |   @ NODE_STR (line: 1)
#         |   +- nd_lit: " zzz"
#         +- nd_next:
#             (null node)

在解析器阶段有两个字符串文字，"aaa "和" zzz":

There are two string literals at the parser stage, "aaa " and " zzz":

#     +- nd_lit: "aaa "
#     ...
#         |   +- nd_lit: " zzz"

检查ObjectSpace确认这些字符串已被实例化:

Inspecting ObjectSpace confirms that these strings have been instantiated:

$ ruby -e '"aaa #{123} zzz"; ObjectSpace.each_object(String) { |s| p s }' | egrep "aaa|zzz"
"\"aaa \#{123} zzz\"; ObjectSpace.each_object(String) { |s| p s }\n"
"aaa 123 zzz"
" zzz"
"aaa "

因此，除非您要创建新的字符串实例(例如，通过将字符串文字赋值给变量)，否则无法检测到字符串的创建.执行代码时已经存在.

So unless you are creating a new string instance (e.g. by assigning the string literal to a variable) you can't detect the string creation. It's already there when the code is being executed.

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