Groovy with Style — GR8Conf Europe 2015

Groovy with Style — GR8Conf Europe 2015

Groovy with Style: tips, tricks, nuggets, style advice for the Groovy developers!

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Guillaume Laforge

June 03, 2015
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Transcript

  1. 3.
  2. 8.
  3. 9.
  4. 10.
  5. 11.
  6. 12.
  7. 13.
  8. 14.
  9. 15.

    <=>

  10. 18.
  11. 19.
  12. 20.
  13. 21.

    15 No semicolons! class Hello {
 private String message =

    'Hello!';
 String greet(String name) {
 "$message, $name speaking";
 } 
 }
 
 print new Hello().greet('Guillaume');
  14. 22.

    15 No semicolons! class Hello {
 private String message =

    'Hello!';
 String greet(String name) {
 "$message, $name speaking";
 } 
 }
 
 print new Hello().greet('Guillaume');
  15. 23.

    16 No semicolons! class Hello {
 private String message =

    'Hello'
 String greet(String name) {
 "$message, $name speaking"
 } 
 }
 
 print new Hello().greet('Guillaume')
  16. 24.
  17. 25.

    18 Public by default public class Hello {
 private static

    String message = 'Hello'
 private String name
 
 public Hello(String name) {
 this.name = name
 }
 public String greet() {
 return "$message, $name speaking"
 } 
 }
  18. 26.

    19 Public by default class Hello {
 private static String

    message = 'Hello'
 private String name
 
 Hello(String name) {
 this.name = name
 }
 String greet() {
 return "$message, $name speaking"
 } 
 } Methods and classes are public by default
  19. 27.

    20 class Hello {
 static String message = 'Hello’
 String

    name
 
 Hello(String name) {
 this.name = name
 }
 String greet() {
 return "$message, $name speaking"
 } 
 } Fields and static fields require visibility
  20. 28.

    20 class Hello {
 static String message = 'Hello’
 String

    name
 
 Hello(String name) {
 this.name = name
 }
 String greet() {
 return "$message, $name speaking"
 } 
 } Fields and static fields require visibility You created both an instance property and a static property!
  21. 29.
  22. 30.

    22 Get rid of the useless ‘def’ class Hello {


    private static String message = 'Hello'
 private def String name
 def Hello(def String name) {
 this.name = name
 }
 public def String greet() {
 def String result = "$message, $name speaking"
 return result
 } 
 }

  23. 31.

    22 Get rid of the useless ‘def’ class Hello {


    private static String message = 'Hello'
 private def String name
 def Hello(def String name) {
 this.name = name
 }
 public def String greet() {
 def String result = "$message, $name speaking"
 return result
 } 
 }

  24. 32.

    23 Get rid of the useless ‘def’ class Hello {


    private static String message = 'Hello'
 private String name
 Hello(String name) {
 this.name = name
 }
 String greet() {
 String result = "$message, $name speaking"
 return result
 } 
 }

  25. 33.

    24 Get rid of the useless ‘def’ class Hello {


    private String message = 'Hello'
 private String name
 Hello(String name) {
 this.name = name
 }
 String greet() {
 def result = "$message, $name speaking"
 return result
 } 
 }
 But it’s fine to use ‘def’ for local variables
  26. 34.
  27. 35.
  28. 36.
  29. 38.

    27 Return is optional too String greet() { 
 "$message,

    $name speaking"
 } But return is fine for early returns, or for clarity of intent
  30. 39.

    28 Optional return for if / else int color(String name)

    {
 if (name == 'red')
 1
 else if (name == 'green')
 2
 else
 -1
 }
  31. 40.

    29 Optional return for switch / case int color(String name)

    {
 switch (name) {
 case 'red': 1; break
 case 'green': 2; break
 default: -1
 }
 }
  32. 41.

    29 Optional return for switch / case int color(String name)

    {
 switch (name) {
 case 'red': 1; break
 case 'green': 2; break
 default: -1
 }
 } Yeah, yeah, ugly semicolon and break…
  33. 42.

    30 Optional return for try / catch boolean isInt(String s)

    {
 try {
 Integer.parseInt(s)
 true
 } catch (NumberFormatException nfe) {
 false
 } finally {
 println 'done'
 }
 }
 
 assert isInt('123') && assert !isInt('abc')
  34. 43.

    30 Optional return for try / catch boolean isInt(String s)

    {
 try {
 Integer.parseInt(s)
 true
 } catch (NumberFormatException nfe) {
 false
 } finally {
 println 'done'
 }
 }
 
 assert isInt('123') && assert !isInt('abc') ‘finally’ blocks don’t return a value
  35. 44.
  36. 50.

    35 Command chains & named arguments check that: wine tastes

    good Parsed as: check(that: wine).tastes(good)
  37. 51.

    36 Trailing closure argument gets out void unless(boolean b, Closure

    c) {
 if (!b) c()
 }
 
 def (speed, limit) = [80, 90]
 
 unless(speed > limit) {
 println "speed up a notch"
 }
  38. 52.

    36 Trailing closure argument gets out void unless(boolean b, Closure

    c) {
 if (!b) c()
 }
 
 def (speed, limit) = [80, 90]
 
 unless(speed > limit) {
 println "speed up a notch"
 } Parsed as: unless(speed > limit, {…})
  39. 53.
  40. 56.
  41. 57.

    41 No need for dumb getters and setters class Person

    {
 private String name
 private int age
 
 void setName(String name) {
 this.name = name
 }
 String getName() {
 this.name
 }
 void setAge(int age) {
 this.age = age
 }
 int getAge() {
 this.age
 }
 }
  42. 58.

    42 No need for dumb getters and setters class Person

    {
 String name
 int age
 }
  43. 59.

    42 No need for dumb getters and setters class Person

    {
 String name
 int age
 } Icing on the cake: add @Immutable or @Canonical
  44. 60.

    43 Use the property notation class Person {
 String name


    int age
 }
 
 def p = new Person(name: 'Guillaume', 
 age: 36)
 assert p.name == 'Guillaume'
 
 p.age = 37
 assert p.age == 37
  45. 61.
  46. 63.

    46 The @Builder transformation import groovy.transform.builder.*
 
 @Builder
 class Person

    {
 String name
 int age
 }
 
 Person.builder() .name('Guillaume') .age(37) .build()
  47. 64.

    46 The @Builder transformation import groovy.transform.builder.*
 
 @Builder
 class Person

    {
 String name
 int age
 }
 
 Person.builder() .name('Guillaume') .age(37) .build() Different strategies available: chained setters, external builder class, type-safe initializer
  48. 65.
  49. 68.
  50. 70.
  51. 71.

    53 Native syntax for data structures def list = [1,

    2, 3]
 def range = 'a'..'b'
 def map = [a: 1, b: 2, c: 3]
 def regex = ~/.*foo.*/
  52. 72.
  53. 76.
  54. 77.

    57 Switch / case on steroids switch(obj) {
 case 123:

    "number 123"; break
 case "abc": "string abc"; break
 case String: "is a string"; break
 case [1, 2, 3]: "in list"; break
 case ~/.*o+.*/: "regex match"; break
 case { it < 3 }: "closure criteria"; break
 default: "unknown"
 }
  55. 78.
  56. 79.

    59 Import aliasing import java.util.List as juList
 import java.awt.List as

    aList
 
 import javax.swing.WindowConstants as WC
  57. 81.
  58. 82.

    62 Groovy Truth assert !( null )
 assert !( ""

    )
 assert !( [] )
 assert !( 0 ) assert new Object()
 assert "string"
 assert [1, 2, 3]
 assert 1234
  59. 83.

    62 Groovy Truth assert !( null )
 assert !( ""

    )
 assert !( [] )
 assert !( 0 ) assert new Object()
 assert "string"
 assert [1, 2, 3]
 assert 1234 False
  60. 84.

    62 Groovy Truth assert !( null )
 assert !( ""

    )
 assert !( [] )
 assert !( 0 ) assert new Object()
 assert "string"
 assert [1, 2, 3]
 assert 1234 False True
  61. 85.

    63 Customize the truth with asBoolean() class Account {
 String

    name
 boolean disabled = false
 
 boolean asBoolean() { !disabled }
 }
 
 assert new Account(name: 'current')
 assert !new Account(name: 'old', disabled: true)
  62. 86.
  63. 87.
  64. 88.

    65 Safe navigation // Java if (order != null) {


    if (order.getCustomer() != null) {
 if (order.getCustomer().getAddress() != null) {
 System.out.println(order.getCustomer().getAddress());
 }
 }
 }
 // Groovy println order?.customer?.address
  65. 89.

    65 Safe navigation // Java if (order != null) {


    if (order.getCustomer() != null) {
 if (order.getCustomer().getAddress() != null) {
 System.out.println(order.getCustomer().getAddress());
 }
 }
 }
 // Groovy println order?.customer?.address Also give more meaningful NPEs!
  66. 90.
  67. 91.

    67 Power Assert def (a, b, c, d) = [10,

    20, 30, 610]
 assert a + b * c == d - 40
  68. 92.

    67 Power Assert def (a, b, c, d) = [10,

    20, 30, 610]
 assert a + b * c == d - 40 Assertion failed:
 
 assert a + b * c == d - 40
 | | | | | | | |
 10| 20| 30| | 570
 610 600 | 610
 false
  69. 93.
  70. 94.

    69 Calling Elvis for default values def result = name

    != null && name.length() > 0 ? name : "Unknown"
 
 def result = name ?: "Unknown"
  71. 95.

    69 Calling Elvis for default values def result = name

    != null && name.length() > 0 ? name : "Unknown"
 
 def result = name ?: "Unknown" Groovy Truth 
 at play here
  72. 96.
  73. 98.

    71 Catch ‘any’ exception try {
 something()
 } catch (any)

    {
 // ...
 } Someone suggested me: catch(emAll)
  74. 99.
  75. 100.

    73 Of the importance of contracts • Use explicit typing

    for • method signatures • properties & fields • Nice for • Java interoperability • documenting your APIs • IDE auto-completion and refactoring
  76. 102.
  77. 103.

    76 Picture credits Style: http://1hdwallpapers.com/wallpapers/my_style.jpg Eurostar: http://www.whatsupwhatson.com/wp-content/uploads/2014/04/Eurostar_3012_Waterloo.jpg Puzzle: http://joyinthecause.org/wp-content/uploads/2014/03/missing-puzzle-piece_00449088.jpg Gems:

    http://www.freewhd.com/blue-gems-wallpaper/ Wise: http://fc00.deviantart.net/fs70/i/2012/044/f/6/three_wise_men_color_by_csoro-d4pmlv2.jpg Ready: http://nameshapers.com/wp-content/uploads/2013/12/Social-Media-Coaching-for-CEOs-Getting-started.jpg Semicolon: http://www.freeimageslive.co.uk/image/view/3944/_original Till death to us part: https://mypencillines.files.wordpress.com/2013/04/img_0171.jpg Public: http://www.levelupliving.com/wp-content/uploads/2012/05/Fear-of-Public-Speaking-image.jpg Contract: https://www.icts.uiowa.edu/sites/default/files/contract.jpg Exception: http://www.quotescover.com/wp-content/uploads/Its-the-exception-that-proves__quotes-by-French-Proverb-77.png Banana: http://texturetaddka.com/wp-content/uploads/2011/10/DSC2008.jpg Elvis: http://natedsanders.com/blog/wp-content/uploads/2013/10/Elvis-Presley-Wallpaper-1280-x-960.jpeg Assert: http://www.itshouldjustworktm.com/wp-content/uploads/2012/03/assert-sign-photoshopped.jpg Compass: https://lh4.ggpht.com/WtY8QL0re9kMssF6q4RopDHC6QEpou7ybQo7qNRjn1X8Iu5uKUZv7huHA_PxPB8iGfs=h900 Safety vest: http://media.nautisports.com/catalog/product/image/gilet-de-sauvetage-gonflable-hydrostatique-hammar-pilot-275-n-avec-harnais-pro-rouge- nav_17452_web_1_1.jpg Class: http://upload.wikimedia.org/wikipedia/en/5/50/A_Class_in_Progress.jpg Aliasing: http://i.imgur.com/JrFly.png Light switch: http://www.hapihour.org/wp-content/uploads/2014/04/lighting-design-wall-light-winsome-designer-light-switches-australia-designer-light- switchesdesigner-light-switches-and-platesdesigner-light-switches-coversdesigner-light-switches-graydesign.jpg Steel structure: http://www.jingtabuilding.com/UploadFiles/sl6.jpg Quotes: http://g.fastcompany.net/multisite_files/fastcompany/poster/2013/09/3018353-poster-1280-quotess3.jpg Setter: http://upload.wikimedia.org/wikipedia/commons/b/b4/Rzesz%C3%B3w_Irish_Red_and_White_Setter_1pl.jpg Argument: http://www.familytreecounseling.com/kathysblog/wp-content/uploads/2014/01/arguing_couple.jpg Equal cupcake: http://static.communitytable.com/wp-content/uploads/2013/04/marriage-equality-cupcakes-ftr.jpg Obama truth: http://upload.wikimedia.org/wikipedia/commons/7/7c/Obama_swearing_in.JPG Quiz: http://a622.phobos.apple.com/us/r30/Purple/v4/df/a9/6e/dfa96e6c-ea9b-ee4c-4d6c-f9edf2775e1d/mzl.exfkkuro.png return: http://legacyofshadow.com/wp-content/uploads/2012/04/no-return-sign.jpg spock: http://trekcore.com/gallery/albums/spock09/spock_pb04.jpg London: http://www.100percentoptical.com/images/2014/10/london.jpg Tie fighter: http://img3.wikia.nocookie.net/__cb20090419001710/uncyclopedia/images/f/fe/Darthvader_tie_fighter.jpg