The document summarizes a presentation on improving template engines. It argues that current template engines are too permissive, leading code bases to break fundamental principles. It demonstrates problems with examples using traditional template engines and shows improvements using StringTemplate and Slippers template engines, which enforce stricter separation of view and model logic for more testable, maintainable code. The presentation aims to convince the audience to consider alternative template engines that make it easier to develop code the right way.

1. Taming of the View
RubyConf India 2010
Sarah Taraporewalla
ThoughtWorks
Sunday, 21 March 2010

2. I will attempt to
convince you that:
Sunday, 21 March 2010

3. I will attempt to
convince you that:
- the current template engines are too
permissive
Sunday, 21 March 2010

4. I will attempt to
convince you that:
- the current template engines are too
permissive
- there are loads of code bases that break
fundamental principles
Sunday, 21 March 2010

5. I will attempt to
convince you that:
- the current template engines are too
permissive
- there are loads of code bases that break
fundamental principles
- you should turn to other template engines
Sunday, 21 March 2010

6. What is wrong with
these examples?
Sunday, 21 March 2010

7. Example 1
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8. Example 2
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9. Example 3
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10. Example 4
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11. AGH! This is really
really easy in Rails3
now!
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12. Controller
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13. Why do we get thin
controllers?
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14. Push vs Pull
http://www.flickr.com/photos/91772025@N00/444044158/ CC BY-ND 2.0
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15. Pull
View Controllers Model
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16. Pull - over time
Controllers Model
View
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17. Push
View Controllers Model
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18. Push - over time
View Model
Controllers
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19. Push - and then
View Controllers Services
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20. What do we want?
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21. Testable Code
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22. Testable Code
Don’t put logic in your views
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23. Single Responsibility
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24. Single Responsibility
Don’t let changes in column
names effect your views
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25. Separation of Concerns
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26. Separation of Concerns
Enforce strict separation of
model and view
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27. How do we improve on
the examples?
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28. Example 1 - Before
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29. Example 1 - Improved
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30. Example 2 - Before
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31. Example 2 - Improved
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32. Example 2 - Improved
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33. Example 3 - Before
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34. Example 4 - Before
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35. Example 3,4 - Improved
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36. Example 3,4 - Improved
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37. If you make it easy to
do the wrong thing, the
wrong thing will be
done
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38. If you make it easy to
do the right thing, the
right thing will be done
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39. Haml
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40. Haml
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41. Haml
Good
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42. Haml
Good
But ...
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43. Haml
Good
But ...
still allows ruby
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44. String Template
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45. StringTemplate
- Strict separation of model & view
- Fits well with functional programming
- Written in Java, .Net, Python
is NOT Turing complete
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46. 1. Create a StringTemplate Object with
the template
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47. 1. Create a StringTemplate Object with
the template
string or file
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48. 2. Set attributes and their values
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49. 3. Call toString() to mash attributes onto
the template
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50. Testable?
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51. Testable? Yes!
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52. Single Responsibility?
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53. Single Responsibility?
Yes!
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54. Separation of
Concerns?
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55. Separation of
Concerns? Yes!
It is the essence of its philosophy
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56. Other cool things...
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57. Templates (Partials)
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58. Iterators
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59. Iterators
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60. Renderers
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61. Localisation
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62. But, we do Ruby
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63. Slippers
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64. Slippers
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65. Slippers & Ramaze
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66. Slippers - Example
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67. Slippers - Example
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68. Slippers - Example
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69. Slippers - Example
index.st
person/index.st
person/age.st
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70. Slippers - Example
person/age_renderer.rb
controller/role_renderer.rb
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71. Slippers - Example
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72. Slippers - Testable?
• Holes are correctly plugged
• Correct instance variables set
• Renderers
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73. Slippers - Testable?
• Holes are correctly plugged
• Correct instance variables set
• Renderers
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74. Slippers - Testable?
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75. Slippers - Testable?
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76. Slippers - Testable?
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77. Slippers - Testable?
• Holes are correctly plugged
• Correct instance variables set
• Renderers
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78. Slippers - Testable?
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79. Slippers - Testable?
Sunday, 21 March 2010

80. Slippers - Testable?
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81. Slippers - Testable?
• Holes are correctly plugged
• Correct instance variables set
• Renderers
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82. Slippers - Testable?
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83. Slippers
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84. Slippers
• Can be found at:
‣ http://slippersRb.com
‣ http://github.com/starapor/slippers
‣ http://gemcutter.org/gems/slippers
• Ramaze view template
‣ http://ramaze.net
Sunday, 21 March 2010

85. Have I convinced you
that:
Sunday, 21 March 2010

86. Have I convinced you
that:
- the current template engines are too
permissive
Sunday, 21 March 2010

87. Have I convinced you
that:
- the current template engines are too
permissive
- there are loads of code bases that break
fundamental principles
Sunday, 21 March 2010

88. Have I convinced you
that:
- the current template engines are too
permissive
- there are loads of code bases that break
fundamental principles
- we should turn to other template engines
Sunday, 21 March 2010

89. questions?
Sunday, 21 March 2010