The Myth of Clean Code

Transcript

1. The Myth Of "Clean Code"
3. 3 Variable naming
4. emp_num 4 employee_number
5. 5 “fault fixing in source code with abbreviated identifiers needs a more methodical approach and abbreviated identifiers are not perceived as major obstacle to fix faults in source code.”
6. 6 “Functions & Classes Should Be Small”
7. 7 “Every function in this program was just two, or three, or four lines long. Each was transparently obvious… That’s how short your functions should be!” - Kent Beck
8. 8 fun fetchProfile() { val response = fetch("my_api_url") if (response.code == 200) { return processSuccess(response) } else { processError(response) } }
9. 9 fun fetchProfile() { val response = fetch("my_api_url") if (response.code == 200) { val responseBody = JSONObject(response.body()) return Profile( name = responseBody["name"], age = responseBody["age"] ) } else { log("fetch fails with responseCode: ${response.code}) Snackbar.show("Fail to get profile data") } }
10. 10 public static String renderPageWithSetupsAndTeardowns( PageData pageData,boolean isSuite ) throws Exception { this.isSuite = isSuite if (isTestPage(pageData)) includeSetupAndTeardownPages(); return pageData.getHtml(); } Actual example from “Clean Code” Book
13. Classitis 13 FileInputStream fileIputStream = new FileInputStream(fileName); try { Reader reader = new BufferedReader(new InputStreamReader(stream, cs)); StringBuilder builder = new StringBuilder(); char[] buffer = new char[8192]; int read; while ((read = reader.read(buffer, 0, buffer.length)) > 0) { builder.append(buffer, 0, read); } return builder.toString(); } finally { stream.close(); }
14. 14 val fileText = File("fileName").buffered().readText()
15. 15 “Interfaces should be designed to be make the common case as simple as possible”
17. Shallow Functions 17 fun addNullValue(key: String) { map[key] = null }
18. Shallow Functions 18 public static String renderPageWithSetupsAndTeardowns( PageData pageData,boolean isSuite ) throws Exception { includeSetupAndTeardownPages if (isTestPage(pageData)) includeSetupAndTeardownPages(pageData, isSuite); return pageData.getHtml(); } private static isTestPage(pageData: PageData) { return pageData.hasAttribute("Test") } Actual example from “Clean Code” Book
19. 19 fun fetchProfile() { val response = fetch("my_api_url") if (response.code == 200) { val responseBody = JSONObject(response.body()) return Profile( name = responseBody["name"], age = responseBody["age"] ) } else { Log("fetch fails with responseCode: ${response.code}) Snackbar.show("Fail to get profile data") } } Deep Functions
20. 20 “It’s more important to have a simple interface than a simple implementation”
21. 21 Don’t Repeat Yourself (DRY)
22. 22 “Duplication may be the root of all evil in software”
23. 23 Premature Abstraction is the root of all evil
24. 24 fun log( level: Level, message: String ) { if (level.isCritical()) { Logger.error(message) } else { Logger.warn(message) } }
25. 25 fun log( level: Level, message: String, throwable: Throwable? ) { if (level.isCritical()) { Logger.error(throwable, message) } else { Logger.warn(message) } } log(Level.Info, "message", Exception("This is not used"))
26. 26 interface IAnaylticsPlugin { trackAction(values: Map<string, any>) trackEvent(values: Map<string, any>) }
27. 27 class AdobeAnalyticsPlugin implements IAnaylticsPlugin { trackAction(values: Map<string, any>) = Adobe.track(...) trackEvent(values: Map<string, any>) = Adobe.track(...) } class FirebaseAnalyticsPlugin implements IAnaylticsPlugin { trackAction(values: Map<string, any>) = { /*DO NOTHING*/ } trackEvent(values: Map<string, any>) = Firebase.log(...) }
28. 28 val analyticsPlugins : Array<IAnaylticsPlugin> = [AdobeAnalyticsPlugin(), FirebaseAnalyticsPlugin()] fun trackEvent(...) { analyticsPlugins.forEach((plugin) => { plugin.trackEvent(values) }) }
29. 29 class AdobeAnalytics { trackAction(values: Map<string, any>) = Adobe.track(...) trackEvent(values: Map<string, any>) = Adobe.track(...) } class FirebaseAnalytics { logEvent(values: Map<string, any>) = Firebase.log(values) }
30. 30 private val adobeAnalytics = new AdobeAnalytics() private val firebaseAnalytics = new FirebaseAnalytics() fun trackAction(...) { adobeAnalytics.trackAction(values) } fun trackEvent(...) { adobeAnalytics.trackAction(values) firebaseAnalytics.logEvent(values) }
31. 31 “Duplication is far cheaper than wrong abstraction”
32. Rule of Three 32 “Three strikes and you refactor”
33. 33 Pass-through functions/variables
34. 34 private WikiPage findInheritedPage(String pageName) throws Exception { return PageCrawlerImpl.getInheritedPage(pageName, testPage); } Actual example from “Clean Code” Book! again! Pass-through functions/variables
35. 35 // On UI SearchScreenViewModel.searchUser("username") // In ViewModel SearchUseCase.execute("username") // In SearchUseCase SearchRepository.searchUser("username") // In SearchRepository SearchNetworkDataSource.searchUser("username") // In SearchNetworkDataSource executeApiCall("https://api/search?query=$username") Pass-through functions/variables
36. 36 // On UI SearchScreenViewModel.searchUser("username") // In ViewModel executeApiCall("https://api/search?query=$username") Pass-through functions/variables
37. 37 class ApplicationInstallCheckViewModel( val appInstance: AppInstance ) { fun isAppInstalled(appId: String) { return appInstance.searchAppWithId(appId) != null } } Pass-through functions/variables
38. 38 class AppInstance { private var instance : AppInstance? static fun getInstance() : AppInstance { if (instance == null) { instance = ... } return instance!! } fun isAppInstalled(appId: String) = searchAppWithId(appId) != null } Singletons
39. 39 val textStyles = getTextStyles() FlightCard(textStyles) { TitleText(textStyles) { Text(textStyles.title) } BuyButton(textStyles) { Text(textStyles.button) } } Context Objects
40. 40 { val textStyles = StyleContext.current() Text(textStyles.title) } Context Objects
41. 41 Function Arguments
42. 42 “The ideal number of arguments for a function is zero (niladic). Next comes one (monadic), followed closely by two (dyadic). Three arguments (triadic) should be avoided where possible. More than three (polyadic) requires very special justification—and then shouldn’t be used anyway.”
43. 43 @Composable fun Text( text: String, modifier: Modifier = Modifier, color: Color = Color.Unspecified, fontSize: TextUnit = TextUnit.Unspecified, fontStyle: FontStyle? = null, fontWeight: FontWeight? = null, fontFamily: FontFamily? = null, letterSpacing: TextUnit = TextUnit.Unspecified, textDecoration: TextDecoration? = null, textAlign: TextAlign? = null, lineHeight: TextUnit = TextUnit.Unspecified, overflow: TextOverflow = TextOverflow.Clip, softWrap: Boolean = true, maxLines: Int = Int.MAX_VALUE, minLines: Int = 1, onTextLayout: ((TextLayoutResult) -> Unit)? = null, style: TextStyle = LocalTextStyle.current ) { ... }
44. 44 @Composable fun Text( text: String, modifier: Modifier = Modifier, color: Color = Color.Unspecified, fontSize: TextUnit = TextUnit.Unspecified, fontStyle: FontStyle? = null, fontWeight: FontWeight? = null, fontFamily: FontFamily? = null, letterSpacing: TextUnit = TextUnit.Unspecified, textDecoration: TextDecoration? = null, textAlign: TextAlign? = null, lineHeight: TextUnit = TextUnit.Unspecified, overflow: TextOverflow = TextOverflow.Clip, softWrap: Boolean = true, maxLines: Int = Int.MAX_VALUE, minLines: Int = 1, onTextLayout: ((TextLayoutResult) -> Unit)? = null, style: TextStyle = LocalTextStyle.current ) { ... }
45. 45 “Interfaces should be designed to be make the common case as simple as possible”
46. Slope-interface API design 46 “Providing multiple APIs at different levels of abstraction allows solving 80% of use cases with a simple API, then 80% of the remaining 20% with a more detailed API, and then the final slice with a low-level API. Each layer is built on top of the next one with a measured reduction in API complexity.” https://jakewharton.com/slope-intercept-library-design/
47. 47 Team structures
48. Conway’s Law 48 Your code structure will mirror the organization structure (Paraphrased)
51. 51 Temporal Decomposition
52. 52 protected static int[] generate(int n) { primes = new int[n]; multiplesOfPrimeFactors = new ArrayList<Integer>(); set2AsFirstPrime(); checkOddNumbersForSubsequentPrimes(); return primes; }
53. 53 fun fetchProfile() { val response = fetch("my_api_url") if (response.code == 200) { return processSuccess(response) } else { processError(response) } }
54. 54 fun fetchProfile() { val response = fetch("my_api_url") if (response.code == 200) { val responseBody = JSONObject(response.body()) return Profile( name = responseBody["name"], age = responseBody["age"] ) } else { log("fetch fails with responseCode: ${response.code}) Snackbar.show("Fail to get profile data") } }
55. 55 Comments
56. 56 “Comments are signs that your code is bad” “Code is a documentation”
57. Comments 57 • Explain the intent • Describe edge cases • Historical context
58. 58 “The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge”