![Mixins:
Fragile
Hierarchies
[½]
Person
Quaker
Nixon
Republican
Pacifist? Y
Votes_for? ??
Pacifist? N
Votes_for? Trump
Pacifist? N
Votes_for? Trump](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-16-320.jpg)
![Mixins:
Fragile
Hierarchies
[2/2]
Person
Republican
Nixon
Quaker
Pacifist? N
Votes_for? Trump
Pacifist? Y
Votes_for? ??
Pacifist? Y
Votes_for? ??](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-17-320.jpg)
![Traits
Specification
require ‘cube’
Adder = Cube.interface {
proto(:sum, [Integer]) { Integer }
}
# Expect methods for parameters.
ProductCalcT = Cube.trait do
def product(a, b)
ret = 0
a.times { ret = sum([ret, b]) }
ret
end
# Enforce input.
requires_interface Adder
end
StatsCalcT = Cube.trait do
def avg(arr)
arr.reduce(0, &:+) / arr.size
end
end](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-22-320.jpg)
![Traits
Creating
Classes
Class = Superclass + State + Traits + Glue
SimpleCalc = Calc.with_trait(ProductCalcT)
sc = SimpleCalc.new
p sc.product(3, 2)
Or
AdvancedCalc = Calc
.with_trait(ProductCalcT)
.with_trait(StatsCalcT)
ac = AdvancedCalc.new
p ac.product(3, 2)
p ac.avg([3, 2, 4])](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-23-320.jpg)
![Traits
Conflict
Resolution [⅓]
ProductCalcT = Cube.trait do
def product(a, b)
ret = 0
a.times { ret = sum([ret, b]) }
ret
end
requires_interface Adder
end
StatsCalcT = Cube.trait do
def product; end
def avg(arr)
arr.reduce(0, &:+) / arr.size
end
end
AdvancedCalc = Calc.with_trait(ProductCalcT).with_trait(StatsCalcT)
AdvancedCalc.new.product(3, 2)
meson10@xps:$ bundle exec ruby traits.rb
/home/meson10/cube/traits.rb:38:in `append_features':
(Cube::Trait::MethodConflict)
#<UnboundMethod:
#<Class:0x005642a0cad580>(#<Module:0x005642a0cb5870>)#product>](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-24-320.jpg)
![ProductCalcT = Cube.trait do
def product(a, b)
ret = 0
a.times { ret = sum([ret, b]) }
ret
end
requires_interface Adder
end
StatsCalcT = Cube.trait do
def product; end
def avg(arr)
arr.reduce(0, &:+) / arr.size
end
end
AdvancedCalc = Calc.with_trait(ProductCalcT)
.with_trait(StatsCalcT, suppress: [:product])
P AdvancedCalc.new.product(3, 2)
meson10@xps:$ bundle exec ruby traits.rb
6
Traits
Conflict
Resolution [⅔]](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-25-320.jpg)
![class CalcImpl
def sum(a)
a.reduce(0, &:+)
end
# Trumps trait.
def product(a, b)
8
end
end
Calc = Cube.from(CalcImpl)
ProductCalcT = Cube.trait do
def product(a, b)
ret = 0
a.times { ret = sum([ret, b]) }
ret
end
requires_interface Adder
end
SimpleCalc = Calc.with_trait(ProductCalcT)
p SimpleCalc.new.product(3, 2)
Traits
Conflict
Resolution
[3/3]](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-26-320.jpg)
![ProductCalcT = Cube.trait do
def product(a, b)
ret = 0
a.times { ret = sum([ret, b]) }
ret
end
requires_interface Adder
end
PolarCalcT = Cube.trait do
def product(a, b)
# Polar implementation
88
end
end
AdvancedCalc = Calc
.with_trait(ProductCalcT)
.with_trait(PolarCalcT, rename: {"product" => "polar_product"})
ac = AdvancedCalc.new
p ac.product(3, 2)
p ac.polar_product(3, 2)
Traits
Aliasing](https://image.slidesharecdn.com/behaviordrivenoop-170118193935/85/Behavior-driven-oop-27-320.jpg)
Behavior driven oop
- 1. Behavior Driven OOP An Introduction to Traits
- 2. Inspiration Traits: Composable Units of Behavior http://bit.ly/2eJfm7h Oogway: Talk: http://expert-talks.in/#designingWithTraitsInJava Talk: https://www.youtube.com/watch?v=Tc6izy_oeus Ruby-Gem: https://github.com/oogway/rubycube
- 3. Primer to Object Oriented Programming.
- 4. Classess Executable entity Behaviour State Template/ Factory for objects Instance generator Type/ Entities Definitions of method & Data. Units of reuse: Inheritance/ Hierarchy. Composition.
- 10. Multiple Inheritance: Duplication + Rigidity Reader A read() SyncReaderA super.r ead() Locker Reader B read() SyncReaderB super.r ead() Locker
- 12. Nixon’s Diamond Quakers are Pacifists, mostly. Republicans are not Pacifists, mostly. Nixon is both a Quaker and a Republican, certainly. Is Nixon a pacifist?
- 15. Mixins: Linearity module A def as_string super + ' Mixin-A' end end module B def as_string super + ' Mixin-B' end end class BaseA def as_string 'BaseA' end end class MyA < BaseA include B include A end $stderr.puts MyA.new.as_string meson10@xps:~/workspace/meson10/traits$ ruby super.rb BaseA Mixin-B Mixin-A
- 16. Mixins: Fragile Hierarchies [½] Person Quaker Nixon Republican Pacifist? Y Votes_for? ?? Pacifist? N Votes_for? Trump Pacifist? N Votes_for? Trump
- 17. Mixins: Fragile Hierarchies [2/2] Person Republican Nixon Quaker Pacifist? N Votes_for? Trump Pacifist? Y Votes_for? ?? Pacifist? Y Votes_for? ??
- 18. Traits
- 19. Traits Building Blocks for Classes. Primitive units of code reuse.
- 20. Specifying Traits Provide method implementations. Methods as parameters. Cannot access State. Cannot alter/maintain State. Flattening property.
- 22. Traits Specification require ‘cube’ Adder = Cube.interface { proto(:sum, [Integer]) { Integer } } # Expect methods for parameters. ProductCalcT = Cube.trait do def product(a, b) ret = 0 a.times { ret = sum([ret, b]) } ret end # Enforce input. requires_interface Adder end StatsCalcT = Cube.trait do def avg(arr) arr.reduce(0, &:+) / arr.size end end
- 23. Traits Creating Classes Class = Superclass + State + Traits + Glue SimpleCalc = Calc.with_trait(ProductCalcT) sc = SimpleCalc.new p sc.product(3, 2) Or AdvancedCalc = Calc .with_trait(ProductCalcT) .with_trait(StatsCalcT) ac = AdvancedCalc.new p ac.product(3, 2) p ac.avg([3, 2, 4])
- 24. Traits Conflict Resolution [⅓] ProductCalcT = Cube.trait do def product(a, b) ret = 0 a.times { ret = sum([ret, b]) } ret end requires_interface Adder end StatsCalcT = Cube.trait do def product; end def avg(arr) arr.reduce(0, &:+) / arr.size end end AdvancedCalc = Calc.with_trait(ProductCalcT).with_trait(StatsCalcT) AdvancedCalc.new.product(3, 2) meson10@xps:$ bundle exec ruby traits.rb /home/meson10/cube/traits.rb:38:in `append_features': (Cube::Trait::MethodConflict) #<UnboundMethod: #<Class:0x005642a0cad580>(#<Module:0x005642a0cb5870>)#product>
- 25. ProductCalcT = Cube.trait do def product(a, b) ret = 0 a.times { ret = sum([ret, b]) } ret end requires_interface Adder end StatsCalcT = Cube.trait do def product; end def avg(arr) arr.reduce(0, &:+) / arr.size end end AdvancedCalc = Calc.with_trait(ProductCalcT) .with_trait(StatsCalcT, suppress: [:product]) P AdvancedCalc.new.product(3, 2) meson10@xps:$ bundle exec ruby traits.rb 6 Traits Conflict Resolution [⅔]
- 26. class CalcImpl def sum(a) a.reduce(0, &:+) end # Trumps trait. def product(a, b) 8 end end Calc = Cube.from(CalcImpl) ProductCalcT = Cube.trait do def product(a, b) ret = 0 a.times { ret = sum([ret, b]) } ret end requires_interface Adder end SimpleCalc = Calc.with_trait(ProductCalcT) p SimpleCalc.new.product(3, 2) Traits Conflict Resolution [3/3]
- 27. ProductCalcT = Cube.trait do def product(a, b) ret = 0 a.times { ret = sum([ret, b]) } ret end requires_interface Adder end PolarCalcT = Cube.trait do def product(a, b) # Polar implementation 88 end end AdvancedCalc = Calc .with_trait(ProductCalcT) .with_trait(PolarCalcT, rename: {"product" => "polar_product"}) ac = AdvancedCalc.new p ac.product(3, 2) p ac.polar_product(3, 2) Traits Aliasing
- 28. Traits Conflict Resolution Class methods >> trait methods. Trait methods >> superclass methods. Method conflicts must be explicitly resolved.
- 29. Traits Issue(s) When two traits are composed, it may be that each requires a semantically different method that happens to have the same name. Consider a trait X that uses two traits Y1 and Y2 , which in turn both use the trait Z . foo provided by Z will be obtained by X twice. The key language design question is: should this be considered a conflict?
- 30. Thank you.
Editor's Notes
- #20: A trait contains methods that implement the behaviour that it provides. A trait may require methods as parameters for the provided Behaviour. Traits cannot specify any state, and never access state directly. Trait methods can access state indirectly, using required methods. The purpose of traits is to decompose classes into reusable building blocks by pro- viding first-class representations for the different aspects of the behaviour of a class. Note that we use the term “aspect” to denote an independent, but not necessarily cross- cutting, concern. Traits differ from classes in that they do not define any kind of state, and that they can be composed using mechanisms other than inheritance.