Defly

A debug tool for Ruby

Transcript

1. Defly
   Debugging and Tracing Tool for Ruby
   http://github.com/eggegg/defly
   

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2. Andrew Liu 劉彥廷
   • College Student
   • Intern @ Cardinalblue
   • eggegg @ github
   • Ruby, iOS, Android
   • andrewliu33@gmail.com
   

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3. gem install defly
   

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4. Defly is for...
   • Trace method calls
   • Trace instance variables
   • Better error messages
   • Inspect the point of error
   

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5. class Warrior
   attr_accessor :hp, :mp
   def sleep
   self.hp += 10
   self.mp += 2
   end
   end
   

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6. class Warrior
   attr_accessor :hp, :mp
   def sleep
   puts "BEFORE: #{@hp}, #{@mp}"
   self.hp += 10
   puts "AFTER ADDING HP: #{@hp}, #{@mp}"
   self.mp += 2
   puts "AFTER ADDING MP: #{@hp}, #{@mp}"
   end
   end
   

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7. class Warrior
   attr_accessor :hp, :mp
   def sleep
   self.hp += 10
   self.mp += 2
   end
   end
   require 'defly'
   Warrior.debug!
   Warrior.new.trace([:hp, :hp=, :mp, :mp=, :sleep],
   [:@hp, :@mp]) do |warrior|
   warrior.hp = 10
   warrior.mp = 20
   warrior.sleep
   end
   

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8. Tracing hp, hp=, mp, mp=, sleep on Warrior instance
   Tracing @hp, @mp on Warrior instance
   <<<<< Warrior#hp=(10) # (irb):14:in `block in irb_binding'
   @hp = 10 # undefined
   @mp = nil # undefined
   >>>>> 10
   <<<<< Warrior#mp=(20) # (irb):15:in `block in irb_binding'
   @mp = 20 # undefined
   >>>>> 20
   <<<<< Warrior#sleep() # (irb):16:in `block in irb_binding'
   <<<<< Warrior#hp() # (irb):7:in `sleep'
   >>>>> 10
   <<<<< Warrior#hp=(20) # (irb):7:in `sleep'
   @hp = 20 # 10 -> 20
   >>>>> 20
   <<<<< Warrior#mp() # (irb):8:in `sleep'
   >>>>> 20
   <<<<< Warrior#mp=(22) # (irb):8:in `sleep'
   @mp = 22 # 20 -> 22
   >>>>> 22
   >>>>> 22
   

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9. NoMethodError
   debugging = nil
   debugging.is_annoying
   irb(main):001:0> require 'bug'
   NoMethodError: undefined method `is_annoying' for nil:NilClass
   from /Users/eggegg/bug.rb:2:in `'
   ...
   bug.rb
   irb
   Where is the bug???
   

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10. irb(main):003:0> require 'defly'
    => true
    irb(main):004:0> require 'bug'
    NoMethodError: undefined method `is_annoying' for nil:NilClass
    bug.rb:2> debugging.<>
    from /Users/andrewliu/bug.rb:2:in `'
    

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11. Inspecting Errors
    class Rocket
    def launch!
    @reason = "Bugs invasion"
    raise "Engine Fail"
    end
    end
    Rocket.debug!
    rocket = Rocket.new
    rocket.watch_error "Engine Fail"
    rocket.launch!
    

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12. >>>>> Error received:
    "Engine Fail"
    >>>>>
    #> @reason
    => "Bugs invasion"
    #>
    Ruby shell (Rib by godfat)
    to inspect errors!
    

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13. Thanks!
    Any Question?
    

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