Readable Code 勉強会 in 仙台 Part 1: 名前を改善する

2014/05/15日に行ったリーダブルコードの勉強会で使用したスライドです。

Transcript

1. Readable Code ษڧձ in ઋ୆ Part 1: ໊લΛվળ͢Δ
2. ࣗݾ঺հ { name: “Տ໺ ߁ོ”, company: “גࣜձࣾηΧΠωοτ”, facebook: “kouno.yasutaka”, favorite: [ “GAE/J”, “Spock”, “D3.js”, ], }
3. AGENDA 1.ͳͥɺಡΊΔίʔυΛॻ͘΂͖ͳͷ͔ʁ 2.͜ͷษڧձͷํ਑ 3.·ͣ͸ɺ໊લΛվળ͠Α͏
4. 1.ͳͥɺಡΊΔίʔυΛ
 ॻ͘΂͖ͳͷ͔ʁ
5. Ձ஋ͷ͋Δίʔυ ࣮ࡍʹಈ͘ίʔυ ʹ ʁ
6. Քಇ͍ͯ͠Δ͚ΕͲ… •υΩϡϝϯτͱίʔυʹ੔߹ੑ͕ͳ͍ •ػೳ௥Ճ΍όάͷमਖ਼͕ࠔ೉ •ӡ༻͕ࠔ೉ •ͦ΋ͦ΋ɺ
 ͳͥಈ͍͍ͯΔͷ͔෼͔Βͳ͍ʘ(^o^)ʗ
7. Ώ͑ʹ
8. ίετʼύϑΥʔϚϯε
9. ಈ͔͘ΒՁ஋͕͋Δͱ͸͍͑ͳ͍
10. Ձ஋ͷ͋Δίʔυͱ͸ • ਖ਼͘͠ಈ࡞͢Δ • ػೳΛ௥Ճɾมߋ͠΍͍͢ • ༰қʹϝϯςφϯεͰ͖Δ
11. Ձ஋ͷ͋ΔίʔυΛॻͨ͘Ίʹ σβΠϯύλʔϯ ςετۦಈ։ൃ ΞϧΰϦζϜ ϑϨʔϜϫʔΫ ΞδϟΠϧ։ൃ
12. ΅ͬͪʹ༏͘͠ͳ͍
13. ໌೔͔Β୭Ͱ΋͙͢ʹ࣮ફͰ͖ͯɺ ্ྲྀɾԼྲྀɾ্ڃऀɾॳ৺ऀΛ໰Θͣɺ ͔͠΋ޮՌ͕ߴ͍ํ๏
14. Ϧʔμϒϧίʔυ
15. ಡΈ΍͍͢ίʔυ͸ Ձ஋ͷ͋ΔίʔυͷୈҰา • ؒҧ͑ʹ͍͘͠ɺؒҧ͍Λݟ͚ͭ΍͍͢ɻ • ແବͳίʔυ΍ίϝϯτɺυΩϡϝϯτʹ
 ࣌ؒɾࢥߟΛୣΘΕͳ͍ɻ • ༏Εͨઃܭ΍ςετͷ͠΍͢͞ʹͭͳ͕Δ • ̋̋͞Μ͡Όͳ͍ͱΘ͔Βͳ͍ίʔυ͕ແ ͘ͳΔ
16. ͓͢͢Ί͸PDF൛ ɹλϒϨοτͰಡΈ΍͍͢B5ຊ Ͳͷݱ৔ʹ΋࣋ͪग़ͤΔ ! ΦϥΠϦʔͷ
 Ebook StoreͰൢചத https://www.oreilly.co.jp/books/9784873115658/ ͜ΕΛಡ΋͏ʂ
17. 2.͜ͷษڧձͷํ਑
18. ͜ͷษڧձͷํ਑ • ະಡऀͷ༧शɾطಡऀͷ෮शͱ͢Δ • ͳΔ΂͘JavaݴޠΛ࢖ͬͯઆ໌͍ͯ͘͠ • ࣗ෼ͷίʔυͷվળ఺Λ஌Δ • ͨ·ʹࢦ͠·͢ͷͰɺշ͓͘Ԡ͍͑ͩ͘͞
19. 3.ཧղ͠΍͍͢ίʔυ
20. ͲͪΒ͕༏Ε͍ͯΔʁ // ύλʔϯ1 int i = 0; while (list.size() > i) { Object element = list.get(i); System.out.println(element); i++; } ! // ύλʔϯ2 for (Object element : list) { System.out.println(element); }
21. ͲͪΒ͕༏Ε͍ͯΔʁ // exponent ࢦ਺, mantissa Ծ਺ // ύλʔϯ1 if (exponent >= 0) { return mantissa * (1 << exponent); } else { return mantissa / (1 << -exponent); } ! // ύλʔϯ2 return exponent >= 0 ? mantissa * (1 << exponent) : mantissa / (1 << -exponent);
22. ίʔυ͸ଞͷਓ͕ ࠷୹࣌ؒͰཧղͰ͖ΔΑ͏ʹ
 ॻ͔ͳ͚Ε͹͍͚ͳ͍ɻ POINT
23. ίʔυ͕୹͍͜ͱ͸ྑ͍͜ͱͩɻ Ͱ΋ɺઈରʹྑ͍ͱ͸ݶΒͳ͍
24. ͲͪΒ͕༏Ε͍ͯΔʁ // ύλʔϯ1 int i = 0; while (list.size() > i) { Object element = list.get(i); System.out.println(element); i++; } ! // ύλʔϯ2 for (Object element : list) { System.out.println(element); }
25. ͲͪΒ͕༏Ε͍ͯΔʁ // exponent ࢦ਺, mantissa Ծ਺ // ύλʔϯ1 if (exponent >= 0) { return mantissa * (1 << exponent); } else { return mantissa / (1 << -exponent); } ! // ύλʔϯ2 return exponent >= 0 ? mantissa * (1 << exponent) : mantissa / (1 << -exponent);
26. ୹͚Ε͹͍͍Θ͚͡Όͳ͍ // ͜Ε͸Կ΍ͬͯΔͷ͔Α͘Θ͔Βͳ͍ assert (((bucket = findBucket(key)) != null) || !bucket.isOccupied()); ! ! // Ͱ΋ɺ͜ΕͳΒΘ͔Δ bucket = findBucket(key); if (bucket != null) assert (!bucket.isOccupied());
27. ίϝϯτ͕͋Δ͓͔͛ͰཧղͰ͖Δ //"hash = (65599 * hash) + c" ͷߴ଎൛ hash = (hash << 6) + (hash << 16) - hash + c;
28. ·ͱΊ ίʔυ͸ଞͷਓ͕ ࠷୹࣌ؒͰཧղͰ͖ΔΑ͏ʹ
 ॻ͔ͳ͚Ε͹͍͚ͳ͍ɻ ! େࣄͳ͜ͱͳͷͰೋճݴ͍·ͨ͠
29. 4.໊લʹ৘ใΛ٧ΊࠐΉ
30. ॻ͍ͯΈΑ͏ʂ ࣍ͷ࢓༷ͷϝιουఆٛΛॻ͍ͯΈ͍ͯͩ͘͞ɻ ίϝϯτ͸͍Γ·ͤΜɻ ! • ࢦఆ͞ΕͨURLʹ͋ΔϑΝΠϧΛऔಘ͢Δ • औಘϑΝΠϧαΠζͷ্ݶ͕ࢦఆͰ͖Δɻ • λΠϜΞ΢τ࣌ؒΛࢦఆͰ͖Δɻ ! • ࣭໰͕͋Ε͹ड͚෇͚·͢ɻ
31. ແ೉ͳ໊લΛཞ༻ͯ͠·ͤΜ͔ʁ get set buf result tmp size str list map hoge obj1, obj2
32. /** WebαΠτͷΠϯλʔϑΣʔε. */ interface WebSite { Page getPage(); } /** WebαΠτͷΠϯλʔϑΣʔεʢվળҊʣ. */ interface WebSite { Page fetchPage(); } Ͳ͔͜Βऔͬͯ͘Δͷʁ
33. /** ೋ෼໦Ϋϥε. */ class BinaryTree { int size(); } /** ೋ෼໦ΫϥεʢվળҊʣ. */ class BinaryTree { int height(); int numNodes(); } ͳΜͷαΠζʁ ߴ͞ʁ ϊʔυͷ਺ʁ
34. /** εϨουΫϥε. */ class Thread { void stop(); } /** εϨουΫϥεʢվળҊʣ. */ class Thread { void kill(); void pause(); // resume()ͰॲཧΛ࠶։ } ڧ੍ऴྃʁɹҰ࣌ఀࢭʁ
35. ໨తʹଈͨ͠ ໌ྎͳ୯ޠΛબ΅͏ POINT
36. γιʔϥεʢྨޠࣙయʣΛ࢖͏ http://thesaurus.com/
37. ΍Γա͗ʹ஫ҙ͠Α͏ class String { // ͨͱ͑͹ɺStringʹ͜Μͳϝιου͕͋ͬͨΒࠞཚͯ͠͠·͏ɻ public String[] split(String regex); public String[] divide(String regex); public String[] partition(String regex); // "boo:and:foo".split(":") > ["boo", "and", "foo"] // "boo:and:foo".divide(":") > ["boo", ":", "and", ":", "foo"] // "boo:and:foo".partition(":") > ["boo", ":and", ":foo"] }
38. ۭڏͳ໊લΛආ͚Δ
39. ̎఺ؒͷڑ཭ΛٻΊΔίʔυΛॻ͘ B C D ߟ͑ํɿ
    
    ϐλΰϥεͷఆཧ
    
    D
    
    B
    
    C ࠲ඪ̍ ࠲ඪ̎
40. // n࣍ݩ্ͷೋ఺ؒͷڑ཭ΛٻΊΔɻྫɿ̎࣍ݩͷ৔߹ pointA = [5, 3] public static double distance(double[] pointA, double[] pointB) { // ೋ఺ͷ࣍ݩ͕ҟͳΔ৔߹͸ඇ਺Λฦ͢ if (pointA.length != pointB.length) return Double.NaN; double result = 0.0; for (int i = 0; i < pointA.length; i++) { result += Math.pow(pointA[i] - pointB[i], 2); } return result; } ̎఺ؒͷڑ཭ΛٻΊΔίʔυ ฏํ $ ͷ··ʂ
41. //n࣍ݩ্ͷೋ఺ؒͷڑ཭ΛٻΊΔɻʢमਖ਼൛ʣ public static double distance(double[] pointA, double[] pointB) { // ೋ఺ͷ࣍ݩ͕ҟͳΔ৔߹͸ඇ਺Λฦ͢ if (pointA.length != pointB.length) return Double.NaN; double squareDistance = 0.0; // ೋ఺ؒͷڑ཭ͷฏํ for (int i = 0; i < pointA.length; i++) { squareDistance += Math.pow(pointA[i] - pointB[i], 2); } return Math.sqrt(squareDistance); // ೋ఺ؒͷڑ཭ͷฏํࠜΛฦ͢ } ̎఺ؒͷڑ཭ΛٻΊΔίʔυʢमਖ਼൛ʣ ฏํͷ··ͳΒόάͱΘ͔Δ
42. resultͷΑ͏ͳ ۭڏͳ໊લΛආ͚Δ POINT
43. ͜ͷtmp͸໰୊ͳ͍ // ࠨӈͷ஋ΛೖΕସ͑Δ if (right < left) { tmp = right; right = left; left = tmp; } ʮҰ࣌తͳ஋ͷஔ͖৔ʯ ͱ͍͏ҙਤ͕໌֬
44. ͜ͷtmp͸μϝ // Ϣʔβʔ৘ใΛจࣈྻԽ String tmp = user.name(); tmp += " " + user.phone_number(); tmp += " " + user.email(); ... template.put("user_info", tmp); tmpͰ͸ͳ͘ɺuserInfo౳ʹ͢΂͖ ΋͠zpMF@JOGPz౳ʹ
    ؒҧ͑ͯ΋ؾ͔ͮͳ͍
45. ϧʔϓΠςϨʔλʔ i, j, k, iter͸ɺ୹͍͚ͲΑ͘ҙຯΛද͍ͯ͠Δɻ for (int i = 0; i < clubs.size(); i++) for (int j = 0; j < clubs[i].members.size(); j++) for (int k = 0; k < users.size(); k++) if (clubs[i].members[k] == users[j]) System.out.println("user[" + j + "] is in club[" + i + "]"); όάɿLͱK͕ٯ Ͱ΋ɺ࣍ͷΑ͏ͳέʔεͰ͸Ͳ͏ͩΖ͏
46. ϧʔϓΠςϨʔλʔ վળɿͳΜͷΠςϨʔλʔ͔໌֬ʹ͠Α͏ // ci = clubs_iter, mi = members_iter, ui = user_iter for (int ci = 0; ci < clubs.size(); ci++) for (int mi = 0; mi < clubs[ci].members.size(); mi++) for (int ui = 0; ui < users.size(); ui++) if (clubs[ci].members[ui] == users[mi]) System.out.println("user[" + mi + "] is in club[" + ci + "]"); όά͕͙͢ʹղΔ
47. tmp, it, resultͷΑ͏ͳ
 ൚༻తͳ໊લΛ࢖͏ͱ͖͸ɺ ૬Ԡͷཧ༝Λ༻ҙ͢Δɻ POINT
48. ۩ମతͳ໊લΛ͔ͭ͏
49. /** ೚ҙͷTCP/IPϙʔτΛαʔό͕ϦοεϯͰ͖Δ͔֬ೝ͢Δ. */ public boolean serverCanStart() { ... } ػೳʹର͠ɺ ϝιου໊͕ந৅త /** ೚ҙͷTCP/IPϙʔτΛαʔό͕ϦοεϯͰ͖Δ͔֬ೝ͢Δ.(मਖ਼൛) */ public boolean canListenOnPort() { ... }
50. —run_locally Φϓγϣϯ ࣗ࡞ϓϩάϥϜͷΦϓγϣϯɻ ௥Ճͷσόοά৘ใΛग़ྗ͢Δ͕ɺಈ࡞͕஗͘ͳΔɻ ৽͍͠ϝϯόʔ͕
 ཧղͰ͖ͳ͍ ϦϞʔτͰ΋σόοά৘ใ ͕΄͍࣌͠͸ʁ ϩʔΧϧͰύϑΥʔ Ϛϯεςετ͢Δ࣌͸ʁ —extra_loggingͳͲɺ΋ͬͱ௚઀తͳ໊લʹ͠Α͏
51. ໊લʹ৘ใΛ௥Ճ͢Δ
52. // ॲཧ࣌ؒͷܭଌ long start = new Date().getTime(); ... long elapsed = new Date().getTime() - start; System.out.println("ಡΈࠐΈ࣌ؒɿ" + elapsed + "ඵ"); ϛϦඵΛอ͍࣋ͯ͠ΔͨΊɺόά //ॲཧ࣌ؒͷܭଌʢमਖ਼൛ʣ long start_ms = new Date().getTime(); ... long elapsed_ms = new Date().getTime() - start_ms; System.out.println("ಡΈࠐΈ࣌ؒɿ" + (elapsed_ms / 1000L) + "ඵ");
53. ϝιουͷԾҾ਺ ୯ҐΛ௥Ճͨ͠ԾҾ਺ start(int delay) delaySecs, delay_secs createCache(int size) sizeMb, size_mb throttleDownload(float limit) maxKbps, max_kbps rotate(float angle) degreesCw, degrees_cw ୯ҐΛ௥Ճͨ͠ྫ
54. ม਺໊ վળޙͷม਺໊ password plaintextPassword comment unescapedComment html htmlUtf8 data dataUrlEnc ॏཁͳଐੑΛ௥Ճͨ͠ྫ όάʹͳΓͦ͏ͳͱ͜Ζ͚ͩ࢖͏ͷ͕ϙΠϯτ
55. ୯Ґ΍ॏཁͳଐੑ͸ ม਺໊ʹ௥Ճͯ͠ ৗʹҙࣝͰ͖ΔΑ͏ʹ͢Δɻ POINT
56. ௕໊͍લΛආ͚Δ
57. newNavigationControllerWrappingViewControllerForDataSourceOfClass() ֮͑ʹ͍͘͠ɺը໘Λ઎ྖ͍͗ͯ͢͠Δ ͜Μͳ໊લ͸ݏͩ
58. POINT ม਺ͷ࢖͍ํʹΑͬͯɺ
 ໊લͷ௕͞Λม͑Δɻ
59. // είʔϓ͕খ͚͞Ε͹୹໊͍લͰ΋͍͍ if (debug) { Map<String, Integer> m = new HashMap<>(); lookUpNamesNumbers(m); System.out.println(m); } ! ! // ΋͠ɺϝϯόม਺΍άϩʔόϧม਺ͩͱmͷ໨త͕෼͔Βͳ͍ lookUpNamesNumbers(m); System.out.println(m);
60. ௕໊͍લΛೖྗ͢Δͷ͸͔ΜͨΜ EclipseΛྫʹڍ͛Δͱ • େจࣈʹΑΔলུه๏ ✦ “LHM”ͱೖྗͯ͠ίʔυิ׬͢Δͱɺ”LinkedHashMap”͕ೖྗ͞ΕΔɻ ✦ “LinH”ͱೖྗͯ͠ίʔυิ׬͢Δͱɺ
 ”LinkedHashMap”ͱ”LinkedHahsSet”͕ީิʹڍ͕Δɻ ! • ίʔυςϯϓϨʔτͷ࢖༻ ✦ “sysout”ͱೖྗͯ͠ίʔυิ׬͢Δͱɺ
 ”System.out.println()”͕ೖྗ͞ΕΔɻ
61. লུͷ࢓ํʹؾΛ͚ͭΔ // ͜ͷলུ͸ɺ৽͍͠ϝϯόʔ͕ཧղͰ͖ΔͩΖ͏͔ʁ class BEManager // BackEndManagerͷུ ϓϩδΣΫτݻ༗ͷ΋ͷ͸লུ͠ͳ͍΄͏͕ྑ͍ ϓϩάϥϚʹͱͬͯҰൠతͳলུ͸ͯ͠΋ྑ͍ // ͜ͷলུ͸ཧղͰ͖Δ eval // evaluation doc // document str // string
62. ໊લͷϑΥʔϚοτͰ ৘ใΛ఻͑Δ
63. جຊ͚ͩͲɺ͓͞Β͍͠Α͏ // ΫϥεɾΠϯλʔϑΣʔε͸େจࣈͰ࢝ΊΔ public class TaskQueue { // ఆ਺(static final)͸େจࣈͱΞϯμʔείΞ public static final int LIMIT_TASK_NUM = 100; // ม਺΍ϝιου͸খจࣈͰ࢝ΊΔ private Queue<Task> tasks; public void addQueue(Task task) { ... } public Object executeQueue() { ... } }
64. ࠓ೔ͷ·ͱΊ
65. ໊લʹ৘ใΛ٧ΊࠐΉʹ͸ • ໌֬ͳ୯ޠΛબͿ ✴ ঢ়گʹԠͯ͡getͰ͸ͳ͘fetch΍downloadΛ࢖͏ • ൚༻తͳ໊લΛආ͚Δ ✴ ໌֬ͳཧ༝͕ͳ͚Ε͹ɺtmp΍resultΛ࢖Θͳ͍ • ۩ମతͳ໊લͰɺৄࡉʹઆ໌͢Δ ✴ serverCanStart()ΑΓcanListenOnPort()ͷ΄͏͕໌֬ • େ੾ͳ৘ใΛ௥Ճ͢Δ ✴ ϛϦඵΛද͢_msΛ෇͚ΔɻੜύεϫʔυΛplaintextPasswordͱ͢Δɻ • είʔϓʹ߹໊ͬͨલΛ෇͚Δ ✴ ୹͍είʔϓͳΒ୹໊͍લͰྑ͍ɻ௕͍είʔϓͳΒ௕ͯ͘΋໌֬ʹɻ • େจࣈ΍ΞϯμʔείΞͳͲʹҙຯΛࠐΊΔ ✴ ྫ͑͹ɺҰ໨Ͱఆ਺ͱղΔΑ͏ͳ໊લ(LIMIT_TASK_NUM)Λ͚ͭΔɻ
66. ղ౴ྫ public InputStream downloadFileAsStream( String httpUrl, int limitSizeMb, int timeoutSecs);
67. ͝ਗ਼ௌɺ͋Γ͕ͱ͏͍͟͝·ͨ͠
68. ࣸਅૉࡐʹ͍ͭͯ ͜ͷࢿྉ͸ɺͺͨͦ͘(http://pakutaso.comʣͷࣸਅૉࡐΛҰ෦ར ༻͍ͯ͠·͢ɻ͜ͷࣸਅΛܧଓͯ͠ར༻͢Δ৔߹͸ɺͺͨͦ͘ ެࣜαΠτ͔Βࣗ͝਎Ͱμ΢ϯϩʔυ͍͔ͯͨͩ͘͠ɺͺͨ͘ ͦͷ͝ར༻ن໿(http://pakutaso.comʣʹಉҙ͍ͯͨͩ͘͠ඞཁ͕ ͋Γ·͢ɻಉҙ͠ͳ͍৔߹͸ࣸਅͷ͝ར༻͸Ͱ͖·ͤΜͷͰ͝ ஫ҙ͍ͩ͘͞ɻ