Hidden loops
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The document discusses the concept of hidden loops in code, which refers to repetitive structures that can obscure readability and maintainability. It outlines the problems associated with hidden loops, methods for identifying and removing them, and presents a refactoring example using a tic-tac-toe game. Finally, it highlights the advantages and disadvantages of the revised design, emphasizing the importance of understanding functional programming concepts.
![2. Make the loop explicit
Map rulesToResult = new HashMap{
{new XWinsRule(), Result.XWins},
{new OWinsRule(), Result.OWins},
{new NotOverGameRule(), Result.GameNotOverYet)},
{new DefaultRule(), Result.Draw)}
};
Result winner(Board board, Map rulesToResult){
for(Rule rule in rulesToResult.keys()){
if(rule.applies(board)
return rulesToResult[rule];
}
}
20](https://image.slidesharecdn.com/hiddenloops-170516084405/85/Hidden-loops-20-320.jpg)
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Hidden loops
- 1. Hidden Loops Alex Bolboacă, @alexboly, [email protected] May 2017 1
- 2. What is it? Why is it a problem? How to remove it Advantages and Disadvantages of the final design To Close. . . 2
- 4. Say whaaa? A repetitive code structure that can be turned into a loop, usually with the help of higher abstraction data structures. 4
- 5. Typical example if(firstCondition)){ // do anything here } if(secondCondition){ // do something else here } if(thirdCondition){ // even something else here } 5
- 6. Equivalent example if(firstCondition)){ // do anything here } else if(secondCondition){ // do something else here } else if(thirdCondition){ // even something else here } 6
- 7. What is else if? if(firstCondition)){ // do anything here } if(!firstCondition && secondCondition){ // do something else here } if(!firstCondition && !secondCondition && thirdCondition){ // even something else here } // Structurally equivalent with the first example 7
- 8. Second equivalent example switch(variable){ case firstCondition: // do anything here break; case secondCondition: // do something else here break; default: // even something else here break; } 8
- 9. Why is it a problem? 9
- 10. Tends to grow in complexity if(firstCondition)){ for(....){ if(...){ .... } } } else if(secondCondition){ if(...){ ... } } 10
- 11. Tends to grow in size if(firstCondition)){ // do anything here } else if(secondCondition){ // do something else here } else if(thirdCondition){ // even something else here } else if .... else if ... 11
- 12. Often violates Open Closed Principle Figure 1: Design entities should be open to extension and closed to modification 12
- 13. It’s a risk Figure 2: Be aware of the risks and ready to respond. Don’t remove all risks today. source: https://www.blackline.com/blog/wp-content/uploads/2014/12/Risk1.jpg 13
- 14. How to decide if it needs to be removed if( numberOfConditionals >= 3 && weExpectToAddMoreConditionals || weHaveTheSamePatternInMorePlacesInCode || judgementCall ){ considerRemovingIt() } 14
- 15. How to remove it 15
- 16. Removal steps 1. Remove similarity 2. Make the loop explicit 3. Refactor for statement 4. (Optional) Make it configurable 16
- 17. An example would be good Figure 3: TicTacToe Board and pieces made of Lego 17
- 18. Decide winner for TicTacToe Result winner(Board board){ if(anyLineFilledWith('x') || anyColumnFilledWith('x') || anyDiagonalFilledWith('x')) return Result.XWins; if(anyLineFilledWith('0') || anyColumnFilledWith('0') || anyDiagonalFilledWith('0')) return Result.0Wins; if(board.notFilledYet()) return Result.GameNotOverYet; return Result.Draw; } 18
- 19. 1. Remove similarity Result winner(Board board){ if(xWinsRule.matchesFor(board)) return Result.XWins; if(0WinsRule.matchesFor(board)) return Result.0Wins; if(notGameOverRule.matchesFor(board)) return Result.GameNotOverYet; return Result.Draw; } 19
- 20. 2. Make the loop explicit Map rulesToResult = new HashMap{ {new XWinsRule(), Result.XWins}, {new OWinsRule(), Result.OWins}, {new NotOverGameRule(), Result.GameNotOverYet)}, {new DefaultRule(), Result.Draw)} }; Result winner(Board board, Map rulesToResult){ for(Rule rule in rulesToResult.keys()){ if(rule.applies(board) return rulesToResult[rule]; } } 20
- 21. 3. Refactor for statement Result winner(Board board, Map rulesToResult){ Entry<Rule, Result> firstItemWhoseRuleMatches = rulesToResults.find{ ruleToResult->( ruleToResult.key.matchesFor(board) ) } return firstItemWhoseRuleMatches.value } 21
- 22. 4. (Optional) Make it configurable • At compile time, use DependencyInjection to inject the map of rules to results • At run time, use plugins or reflection to instantiate rules and a configuration file 22
- 23. Advantages and Disadvantages of the final design 23
- 24. Advantages • Short methods • Easy to change: • To add a new rule, create a new class and add an object of that class to the map • No change in winner() function to configure the algorithm for another board & set of rules • Follows Open Closed Principle and Single Responsibility Principle • Very easy to unit test in isolation 24
- 25. Disadvantages • Requires developers to understand functional constructs • In this particular case, it has an internal logical coupling: rules have to be logically exclusive. Can deal with this by using single() instead of first() or by using a smarter map • Uses higher level abstractions(rules, result) that can be harder to understand depending on context 25
- 26. To Close. . . 26
- 27. Recap • Hidden loops is a pervasive code smell • Like any smell, it points to potential problems, it doesn’t mean it should always be removed • When removed, you should obtain code that is more easily extensible and testable • But you need to know functional constructs and be careful when changing code. But you have tests, don’t you? :) 27
- 28. Find Me Twitter: alexboly LinkedIn: https://www.linkedin.com/in/alexandrubolboaca/ Blog: http://alexbolboaca.ro Mozaic Works Blog: https://mozaicworks.com/blog eventriX: https://eventrix.co/s/alexandru-bolboaca-56 LeanPub: https://leanpub.com/u/alexbolboaca 28
- 29. Q&A 29