Szymon Szymański: Każdy o nich słyszał, ale niekoniecznie stosował, a co dopiero widział dobrze zakodzone – co może być trudnego w pisaniu wyjątków? Samo pisanie może i nie jest trudne, ale zaprojektowanie ich w taki sposób, aby przynosiły wartość projektowi, to już ciężka sztuka – szczególnie w PHP. Na tej prezentacji dowiesz się, dlaczego ludzie nie pogłębiają wiedzy na temat wyjątków oraz jak można identyfikować miejsca, w których wyjątek jest potrzebny, a w których niekoniecznie. No i oczywiście poznasz KILKA PROSTYCH TRIKÓW na zwiększenie przydatności wyjątków.

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ExceptionDesign
EXCEPTION DESIGN
THE ART OF MAKING DEBUGGING MORE ACCURATE

2. SZYMON ZBIGNIEW SZYMAŃSKI
HEAD OF PHP AT THE SOFTWARE HOUSE

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WHY EXCEPTIONS?
Wasn’t there anything better?

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LET’S INTRODUCE…

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RON!

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FILESYSTEM
ABSTRACTION
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WHY THIS OCCURS?

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Easy to start!
Historical baggage
"
Outdated community habits#

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LOAN CALCULATOR

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WHERE’S THE
EXCEPTION?

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Not happy path$
Improve readability
%

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Problem’s likelihood&
Business or app severity
'

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DOCUMENT SIGNING

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BREAKDOWN
PROBLEM
REASON
No obvious reason why this happened
NAME
Really generic for a task specific piece of
business logic
NOT VERY HELPFUL
The best thing we can do is just log the event
and investigate later
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LET’S FIX IT!

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BREAKDOWN
PROBLEM
REASON
No obvious reason why this happened
NAME
Really generic for a task specific piece of
business logic
NOT VERY HELPFUL
The best thing we can do is just log the event
and investigate later
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WAIT!Isn’t this tooooo verbose?

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CREATING EXCEPTIONS

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CPS(R)
CONTEXT
Be aware of your programming context
PROBLEM
Notice the problem which you want to highlight
SOLUTION (REASON)
Present what needs to be fixed
or
pass something helpful for further debugging
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EXAMPLES

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Top-up prepaid account system(
User account is inactive
❗
Pass the reason code*

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Custom query defined in a config file(
Unrecognized token found in the string
❗
Pass the place where the token starts*

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WHY?

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Adds to „Code is poetry”
Easier problem diagnose
Better problem understanding
Faster problem solving

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KEEP IN MIND

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HOW TO MAKE THINGS
MORE OBVIOUS
CHAINING
3737

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PEOPLE TEND TO
FORGET
THINGS
EXCEPTIONS ARE STILL
OBJECTS
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SOMEBODY WILL READ IT
DON’T OVER DO IT
THINK
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SUMMARY

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WHAT HAVE WE
LEARNED?
SUMMARY
HELPFUL TOOL
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THERE’RE OTHER
MECHANISMS
HOW TO PLACE THEM
HOW TO CREATE THEM
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WHY THEY’RE HELPFUL

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RESULT OBJECT

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PROMISED BONUS

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45. THANK YOU!