I have the following script in a file called foo.rb
def foo(msg)
msg
end
def bar
thing = 123
thing
end
debugger
p foo(:hai)
I run the program in debug mode, like so:
ruby --debug -r debug foo.rb
Notice I make sure the stdlib debug is loaded via -r and I also put the ruby environment into debug mode using --debug
So the first output I get is unexpected:
Debug.rb
Emacs support available.
/Users/M/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:57: RUBYGEMS_ACTIVATION_MONITOR.enter
After that, if I press c to 'continue' the program ends with the following error:
Exception `NameError' at foo.rb:10 - undefined local variable or method `debugger' for main:Object foo.rb:10:in `<main>': undefined local variable or method `debugger' for main:Object (NameError)
Can anyone tell me what I'm doing wrong, and how to actually get debug mode to recognise the relevant debugger command (if that's even the correct command to be using; the docs aren't clear at all on this)
Note: I'm not interested in using 3rd party gems in this instance (e.g. pry or ruby-debug). I'm only interested in understanding how to use the stdlib debugger that comes with Ruby
Update
Since this question was answered, I've gone ahead and created a gist for future reference. For anyone stumbling across this thread you might find it useful: https://gist.github.com/Integralist/5658cb218bb50494a1fa
Don't use -r. The entire mechanism by which an interactive debugging sessions is loaded is by the literal line of code require 'debug'.
Your code should look like this:
def foo(msg)
msg
end
def bar
thing = 123
thing
end
require 'debug'
p foo(:hai)
And you should run the program by simply typing ruby <program_name>.rb.
Related
I want to create a gem to filter warnings in Ruby, and I'd like to do this for "syntax" and "runtime" warnings. I am struggling to work out how its possible to filter the syntax level warnings (or if this possible)
For example, if I run the following script
# myscript.rb
#blah
with ruby -w myscript.rb
myscript.rb:1: warning: possibly useless use of a variable in void context
myscript.rb:1: warning: instance variable #blah not initialized
Now, imagine this is part of a larger project. I would like to filter out any warnings from myscript. How would I go about doing this? Runtime errors would be easy to filter using silence_warnings style code from ActiveSupport https://github.com/rails/rails/blob/3be9a34e78835a8dafc3438f60afb412613773b9/activesupport/lib/active_support/core_ext/kernel/reporting.rb
But I don't know how (or if it's possible) to hook into Rubys syntax level warnings, as it seems to be they'd be run before you have the chance to monkey patch anything. All I can think of is to wrap the ruby script in another process which will filter all the warnings. For example:
myfilterprogram ruby -w myscript.rb which would then catch anything printed to STDERR and filter accordingly.
You may not be able to monkey patch before the main file is read, but you can make your main file call subfiles after doing monkeypatching.
myruby (executable)
#!/usr/bin/env ruby
module Kernel
def warn *args
args # => captured warnings
end
end
load ARGV[0]
Usage is:
myruby foo.rb
I'm working on an application that's a glorified wrapper around irb, and I would like to override the "help" command (which by default seems to be an alias to irb_help). I'm using the approach of executing the following code before allowing the user to do anything in the prompt:
class << self
def help
my_custom_help
end
end
While this seems to work, I get an annoying warn message every time I start the application:
irb: warn: can't alias help from irb_help.
Is there any way to suppress this warning message?
The ruby debugger does not halt on breakpoints I set in files different from the on the execution starts in. For example, consider these two files, foo.rb:
# foo.rb
class Foo
def bar
puts "baz"
end
end
and main.rb:
# main.rb
require './foo'
Foo.new.bar
I start debugging using ruby -r debug .\main.rb. Now, when I try to set a breakpoint on a specific line in another file using b ./foo.rb:4, I get the message Set breakpoint 1 at foo.rb:4, but when I cont, the program executes to the end, and the debugger never halts. However, if I break on a line in main.rb, e.g. b ./main.rb:3, or a method, e.g. b Foo.bar, the debugger halts as expected.
Why doesn't the debugger halt at breakpoints in files other than the main file?
Update: I have tried this with Ruby 1.9.3 on Windows 7 as well as OS X 10.8; it doesn't work in either environment.
I have also just realized that the debugger quits after the script has run till the end: I start debugging main.rb, use cont, then baz is printed on the console and I'm right back in the shell. Is this the expected behaviour, or might the debugger have crashed?
Wow, that is weird. Not sure if this helps, but maybe you could do this. Step over the require with next so that Foo is loaded then
b Foo:bar
that should at least break on bar
Doing the Ruby Koans, in the file about_symbols at line 88, I'm not sure of the answer.
This is the code:
def test_symbols_cannot_be_concatenated
# Exceptions will be pondered further farther down the path
assert_raise(what should i put?) do
:cats + :dogs
end
The point of the Ruby Koans is to learn by reading and trying things out.
Open up a terminal and start irb. Then try using the + operator on two symbols. Check the error you get and substitute it as appropriate in the Koans file.
Assuming that your prompt ends in $, that will look something like this:
$ irb
irb(main):001:0> :cats + :dogs
The answer you need will be clear pretty quickly in the error that irb spits out.
To go through step by step in case your completely new to Ruby you could try:
Open up a terminal
Type irb at your prompt to get to the interactive ruby prompt
This is where you can quickly try out different Ruby things
Type the command in question :cats + :dogs
Review the output which will look like
NoMethodError: undefined method `+' for :cats:Symbol
from (irb):1
The name of the exception thrown which is what you are looking for is the first thing e.g. NoMethodError
I have taken this example exactly from the Ruby Cookbook. Unfortunately for me, like a whole lot of the examples in that book, this one does not work:
my file (Find.rb - saved both locally and to Ruby\bin):
require 'find'
module Find
def match(*paths)
matched=[]
find(*paths) { |path| matched << path if yield path }
return matched
end
module_function :match
end
I try to call it this way from IRB, according to the example the book provides:
irb(main):002:0> require 'Find'
=> false
irb(main):003:0> Find.match("./") { |p| ext = p[-4...p.size]; ext && ext.downcase == "mp3" }
It SHOULD return a list of mp3 files in my recursive directory. Instead, it does this:
NoMethodError: undefined method `match' for Find:Module
from (irb):3
from C:/Ruby192/bin/irb:12:in `<main>'
What gives? I'm new at this (although I MUST say that I'm farther along with Python, and much better at it!).
How can I get IRB to use my method?
I ran into this with irb on a Mac running Snow Leopard while using the default version of ruby (and irb of course) installed with OS X. I was able to get past it by including the module in IRB after loading the module or in the file after the module definition.
include module_name
I'm not sure if this is a defect or known behavior.
The only explanation is that the code you posted is not the code you are running, since both carefully reading it and simply cut&paste&running it shows absolutely no problems whatsoever.
What directory are you calling IRB from? Try calling it from the directory where your find.rb file is located. Also, I don't know if it makes any difference but convention is to name the file the lowercase version of the module / class. So the module would be Find and the file name would be find.rb. You shouldn't need the require call in the file itself.
So, start your command prompt window, cd into the directory that contains find.rb and run irb. In IRB you should be able to require "find" and it should return true. From there you should be able to call Find.match.
I know this question is already 3 years old, but since this is the first hit on google for the problem, and I had been banging my head against the wall all afternoon with the same problem doing the tutorial here: http://ruby.learncodethehardway.org/book/ex25.html, here goes: the function definition in the module should read
module Find
def Find.match(*paths)
...
end
end