Is there a way to access everything in the symbol table in Ruby? I want to be able to serialize or otherwise save the current state of a run of a program. To do this, it seems I need to be able to iterate over all the variables in scope.
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1If you don't mind me asking,what are you using this for ? – Geo Feb 02 '09 at 19:03
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I'm using it for this: http://stackoverflow.com/questions/199603/how-do-you-stringize-serialize-ruby-code Basically, no one answered my question good enough, so before offering bounty (which would make me lose rep), I thought I'd break it out into this sub-question and figure out the answer myself. – Jonathan Tran Feb 02 '09 at 22:27
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I think he comes from a perl background , and that he would like to obtain all the variables defined in a script and serialize them . This way , when he'll load the file , he'll get them back . I'm still searching about how to get a list of the variables , but serialization will be made using Marshal.dump and reading them back will be made with Marshal.load . I'll edit the post once I find out how to get a list of all defined variables .
EDIT : found it!
You can get a list of all variables by calling these methods :
local_variablesglobal_variables
And if you haven't already got your serialization code , I would suggest something like this:
- create a class or a Struct instance that holds a variable name and the value of the variable and add them in an array :
local_variables.each {|var| my_array << MyVarObject.new(var,eval(var)) } # eval is used to get the value of the variable
and then serialize the array :
data = Marshal.dump(my_array)
File.open("myfile.ser","w") do |file|
file.puts data
end
Geo
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Be careful: you have to initialize my_array outside the loop, and as a result it will be included when you iterate over local_variables. You should add "unless var == 'my_array'" just before the closing curly brace to ignore it. – Bkkbrad Feb 02 '09 at 23:53
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If I have understood your question properly - that you would like to see all the symbols in your program then the following should do the trick:
puts Symbol.all_symbols.inspect
The “all_symbols” class method will return an Array of every Symbol currently in the program.
David Grayson
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andHapp
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Yes, this is true. Interestingly, it returns symbols that are not defined as well: `ZZZ` is not defined. `ZZZ;Symbol.all_symbols` includes `ZZZ`. – B Seven Jul 07 '15 at 00:26
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@BSeven "Interestingly, it returns symbols that are not defined as well" It actually doesn't. The mere act of trying to call `ZZZ` is like calling `self.class.const_get(:ZZZ)` (where `self` is the [`main` object](https://stackoverflow.com/q/917811/3141234)). The `ZZZ` symbol is created in that process, even if the subsequent `const_get` fails. – Alexander Mar 17 '21 at 16:16
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@BSeven I encountered a similar issue when trying to look up if a symbol already exists in the symbol table with `Symbol.all_symbols.include?(:foo)`. Naturally, the mere mentioning of `:foo` creates it, so that always evaluates to false. You can work around it with something like `Symbol.all_symbols.find { |sym| sym.to_s == "foo" }` – Alexander Mar 17 '21 at 16:17
