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Ruby Decorators using BasicObject
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require "money" | |
class Decorator < BasicObject | |
undef_method :== | |
def initialize(component) | |
@component = component | |
end | |
def method_missing(name, *args, &block) | |
@component.send(name, *args, &block) | |
end | |
def send(symbol, *args) | |
__send__(symbol, *args) | |
end | |
end | |
class Cream < Decorator | |
def cost | |
@component.cost + ::Money.new(50, "USD") | |
end | |
end | |
class Sugar < Decorator | |
def cost | |
@component.cost + ::Money.new(20, "USD") | |
end | |
end | |
class Coffee | |
def cost | |
::Money.new(200, "USD") | |
end | |
def origin | |
"Columbia" | |
end | |
end |
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describe Coffee do | |
its(:cost) { should == 2 } | |
its(:origin) { should == "Columbia" } | |
it { should be_an_instance_of(Coffee) } | |
end | |
describe "Coffee with Sugar" do | |
let(:coffee) { Coffee.new } | |
subject { Sugar.new(coffee) } | |
it { (subject == coffee).should be_true } | |
its(:cost) { should == 2.2 } | |
its(:origin) { should == "Columbia" } | |
its(:object_id) { should == coffee.object_id } | |
its(:class) { should == coffee.class } | |
it { should be_an_instance_of(Coffee) } | |
end | |
describe "Coffee with two Sugar" do | |
let(:coffee) { Coffee.new } | |
subject { Sugar.new(Sugar.new(coffee)) } | |
it { (subject == coffee).should be_true } | |
its(:cost) { should == 2.4 } | |
its(:origin) { should == "Columbia" } | |
its(:object_id) { should == coffee.object_id } | |
its(:class) { should == coffee.class } | |
it { should be_an_instance_of(Coffee) } | |
end | |
describe "Coffee with Sugar and Cream" do | |
let(:coffee) { Coffee.new } | |
subject { Sugar.new(Cream.new(coffee)) } | |
it { (subject == coffee).should be_true } | |
its(:cost) { should == 2.7 } | |
its(:origin) { should == "Columbia" } | |
its(:object_id) { should == coffee.object_id } | |
its(:class) { should == coffee.class } | |
it { should be_an_instance_of(Coffee) } | |
end |
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http://robots.thoughtbot.com/post/14825364877/evaluating-alternative-decorator-implementations-in