Debugging with pry
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Pry is a powerful alternative to the standard IRB shell for Ruby that provides features like syntax highlighting, plugin support, and runtime invocation. It allows debugging Ruby code through its interactive read-eval-print loop (REPL) and magic commands. These magic commands include ls to list methods, show-source to view method source code, show-doc to view documentation, breakpoints, and more. Pry can help with test-driven development by allowing quick testing and fixing of code.
![Pry magics
ls
[1] pry(main)> ls
self.methods: inspect to_s
locals: _ __ _dir_ _ex_ _file_ _in_ _out_ _pry_
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-13-320.jpg)
![Pry magics
ls
[1] pry(main)> ls Kernel
constants: RUBYGEMS_ACTIVATION_MONITOR
Kernel.methods:
Array Rational abort block_given? exit global_variables open putc require sprintf trace_var
Complex String ap caller exit! iterator? p puts require_relative srand trap
Float __callee__ at_exit caller_locations fail lambda pp raise select syscall untrace_var
Hash __dir__ autoload catch fork load print rand set_trace_func system warn
Integer __method__ autoload? eval format local_variables printf readline sleep test
Pathname ` binding exec gets loop proc readlines spawn throw
Kernel#methods:
!~ clone frozen? kind_of? public_methods tainted?
<=> debugger hash method public_send tap
=== define_singleton_method inspect methods remove_instance_variable to_enum
=~ display instance_of? nil? respond_to? to_s
ai dup instance_variable_defined? object_id send trust
awesome_inspect enum_for instance_variable_get pretty_inspect singleton_class untaint
awesome_print eql? instance_variable_set private_methods singleton_method untrust
byebug extend instance_variables protected_methods singleton_methods untrusted?
class freeze is_a? public_method taint
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-14-320.jpg)
![Pry magics
$ - show-source
[1] pry(main)> $ Kernel#puts
From: io.c (C Method):
Owner: Kernel
Visibility: private
Number of lines: 8
static VALUE
rb_f_puts(argc, argv)
int argc;
VALUE *argv;
{
rb_io_puts(argc, argv, rb_stdout);
return Qnil;
}
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-15-320.jpg)
![Pry magics
$ - show-source
[1] pry(main)> $ Hash
From: /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/pp.rb @ line 369:
Class name: Hash
Number of lines: 9
class Hash # :nodoc:
def pretty_print(q) # :nodoc:
q.pp_hash self
end
def pretty_print_cycle(q) # :nodoc:
q.text(empty? ? '{}' : '{...}')
end
end
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-16-320.jpg)
![Pry magics
? - show-doc
[1] pry(main)> ? Object
From: /home/vagrant/.rvm/gems/ruby-2.1.3/gems/awesome_print-1.2.0/lib/awesome_print/core_ext/object.rb @ line 1:
Class name: Object
Number of monkeypatches: 6. Use the `-a` option to display all available monkeypatches
Number of lines: 5
...
...
...
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-17-320.jpg)
![Pry magics
break
[1] pry(main)> break method_name
Breakpoint 1: /path/to/file.rb @ line 1 (Enabled):
...
...
...
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-18-320.jpg)
![Pry magics
try-again
[1] pry(main)> try-again
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-19-320.jpg)
![Pry magics
step/next
[1] pry(main)> step
[2] pry(main)> next
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-20-320.jpg)
![Pry magics
play
[1] pry(main)> play -l 1
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-21-320.jpg)
![Pry magics
edit [OPTIONS]
4 -e Open editor on last exception raised
4 -m Open editor on a given method
4 -c Open editor on current method
[1] pry(main)> edit -m method_name
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-22-320.jpg)
![Pry magics
up
[1] pry(main)> up
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-23-320.jpg)
![Pry magics
down
[1] pry(main)> down
[2] pry(main)>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-24-320.jpg)
![Pry magics
@ - whereami
[1] pry(Kernel):1> cd Kernel#puts
[2] pry(Kernel):2> @
Inside Kernel.
[3] pry(Kernel):2>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-25-320.jpg)
![More pry magics
wtf - _ex_.backtrace
[1] pry(Kernel):1> wtf?
...
...
...
[2] pry(Kernel):2>
Murilo Capanema - 2015](https://image.slidesharecdn.com/debuggingwithpry-150615223000-lva1-app6892/85/Debugging-with-pry-27-320.jpg)
Debugging with pry
- 1. Debugging with pry ❤ Murilo Capanema - 2015
- 2. Who Am I? GitHub: mcapanema BankFacil (We are Hiring!) Murilo Capanema - 2015
- 3. What is pry ? Pry is a powerful alternative to the standard IRB shell for Ruby. Murilo Capanema - 2015
- 4. Why pry ? Features: 4 syntax highlighting; 4 flexible plugin architecture; 4 runtime invocation and source and documentation browsing; Murilo Capanema - 2015
- 5. Why not to use pry ? Murilo Capanema - 2015
- 6. Murilo Capanema - 2015
- 7. What really is pry ? One line of ruby: def repl loop{ puts eval $stdin.readline} end Murilo Capanema - 2015
- 8. A little bit of REPL Read Eval Print Loop Murilo Capanema - 2015
- 9. A little bit of REPL REPL with Tests 4 REPL first !; 4 Record what the code should do "; 4 Write a code that works first time #; Murilo Capanema - 2015
- 10. Why REPL ? REPL or Debugger Driven Development helps you to reach a code that works pretty quickly Murilo Capanema - 2015
- 11. Backing to pry require 'pry' binding.pry Murilo Capanema - 2015
- 12. Pry and his friends 4 pry-stack-explorer; 4 pry-debugger; 4 pry-rescue; 4 pry-doc; 4 pry-git; 4 help Murilo Capanema - 2015
- 13. Pry magics ls [1] pry(main)> ls self.methods: inspect to_s locals: _ __ _dir_ _ex_ _file_ _in_ _out_ _pry_ [2] pry(main)> Murilo Capanema - 2015
- 14. Pry magics ls [1] pry(main)> ls Kernel constants: RUBYGEMS_ACTIVATION_MONITOR Kernel.methods: Array Rational abort block_given? exit global_variables open putc require sprintf trace_var Complex String ap caller exit! iterator? p puts require_relative srand trap Float __callee__ at_exit caller_locations fail lambda pp raise select syscall untrace_var Hash __dir__ autoload catch fork load print rand set_trace_func system warn Integer __method__ autoload? eval format local_variables printf readline sleep test Pathname ` binding exec gets loop proc readlines spawn throw Kernel#methods: !~ clone frozen? kind_of? public_methods tainted? <=> debugger hash method public_send tap === define_singleton_method inspect methods remove_instance_variable to_enum =~ display instance_of? nil? respond_to? to_s ai dup instance_variable_defined? object_id send trust awesome_inspect enum_for instance_variable_get pretty_inspect singleton_class untaint awesome_print eql? instance_variable_set private_methods singleton_method untrust byebug extend instance_variables protected_methods singleton_methods untrusted? class freeze is_a? public_method taint [2] pry(main)> Murilo Capanema - 2015
- 15. Pry magics $ - show-source [1] pry(main)> $ Kernel#puts From: io.c (C Method): Owner: Kernel Visibility: private Number of lines: 8 static VALUE rb_f_puts(argc, argv) int argc; VALUE *argv; { rb_io_puts(argc, argv, rb_stdout); return Qnil; } [2] pry(main)> Murilo Capanema - 2015
- 16. Pry magics $ - show-source [1] pry(main)> $ Hash From: /home/vagrant/.rvm/rubies/ruby-2.1.3/lib/ruby/2.1.0/pp.rb @ line 369: Class name: Hash Number of lines: 9 class Hash # :nodoc: def pretty_print(q) # :nodoc: q.pp_hash self end def pretty_print_cycle(q) # :nodoc: q.text(empty? ? '{}' : '{...}') end end [2] pry(main)> Murilo Capanema - 2015
- 17. Pry magics ? - show-doc [1] pry(main)> ? Object From: /home/vagrant/.rvm/gems/ruby-2.1.3/gems/awesome_print-1.2.0/lib/awesome_print/core_ext/object.rb @ line 1: Class name: Object Number of monkeypatches: 6. Use the `-a` option to display all available monkeypatches Number of lines: 5 ... ... ... [2] pry(main)> Murilo Capanema - 2015
- 18. Pry magics break [1] pry(main)> break method_name Breakpoint 1: /path/to/file.rb @ line 1 (Enabled): ... ... ... [2] pry(main)> Murilo Capanema - 2015
- 19. Pry magics try-again [1] pry(main)> try-again [2] pry(main)> Murilo Capanema - 2015
- 20. Pry magics step/next [1] pry(main)> step [2] pry(main)> next Murilo Capanema - 2015
- 21. Pry magics play [1] pry(main)> play -l 1 [2] pry(main)> Murilo Capanema - 2015
- 22. Pry magics edit [OPTIONS] 4 -e Open editor on last exception raised 4 -m Open editor on a given method 4 -c Open editor on current method [1] pry(main)> edit -m method_name [2] pry(main)> Murilo Capanema - 2015
- 23. Pry magics up [1] pry(main)> up [2] pry(main)> Murilo Capanema - 2015
- 24. Pry magics down [1] pry(main)> down [2] pry(main)> Murilo Capanema - 2015
- 25. Pry magics @ - whereami [1] pry(Kernel):1> cd Kernel#puts [2] pry(Kernel):2> @ Inside Kernel. [3] pry(Kernel):2> Murilo Capanema - 2015
- 26. Debugging 4 Reproduce locally; 4 Find the problem; 4 Fix it; Murilo Capanema - 2015
- 27. More pry magics wtf - _ex_.backtrace [1] pry(Kernel):1> wtf? ... ... ... [2] pry(Kernel):2> Murilo Capanema - 2015
- 29. Fin GitHub: mcapanema Seriously We are Hiring! Murilo Capanema - 2015