Debugging

Presentation about debugging for people just learning to program.

Transcript

1. Wojciech
   @sharnik
   haikuco.de
   

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2. Programming
   is like riding a bike.
   

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3. Except the bike is on
   fire and you're on
   fire and everything
   is on fire and you're
   actually in hell.
   

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5. Main programming tasks:
   » Adding bugs
   » Removing bugs
   

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6. Debugging
   

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7. Know
   what you're
   trying to do
   

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8. Inputs -> Program -> Outputs
   Calculator.add(2, 3)
   # => 5
   

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9. Workflow
   

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10. Reproduce the
    error
    

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11. Make a
    hypothesis
    

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12. Fix
    

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13. Profit
    

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14. If that didn't help,
    rollback
    

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15. Techniques
    

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16. Puts debugging
    class Calculator
    def add(a, b)
    puts a
    puts b
    a + b
    end
    end
    result = Calculator.new.add(2, 3)
    puts result
    

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17. strings vs numbers
    ruby -e "x = 3; puts x"
    # => 3
    ruby -e "x = '3'; puts x"
    # => 3
    ruby -e "x = 3; puts x.inspect"
    # => 3
    ruby -e "x = '3'; puts x.inspect"
    # => "3"
    

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18. p: shorter puts X.inspect
    class Calculator
    def add(a, b)
    p a
    p b
    a + b
    end
    end
    result = Calculator.new.add(2, 3)
    p result
    

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19. debugger: pry + byebug
    require 'pry-byebug'
    class Calculator
    def add(a, b)
    binding.pry
    a + b
    end
    end
    Calculator.new.add(2, 3)
    

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20. Strategies
    

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21. "Wolf fence"
    algorithm
    

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22. Rubber duck
    debugging
    

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23. Practice
    

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24. Exercise
    gist.github.com/sharnik/2aedd681e6bcf81a7697
    Remember
    » understand expectations
    » pinpoint where the bug is
    » find what the bug is
    » fix it
    

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