看完文章http://jeffkreeftmeijer.com/2011/method-chaining-and-lazy-evaluation-in-ruby/ ,我开始寻找更好的方法链和惰性求值解决方案。
我想我已经用以下五个规范概括了核心问题;谁能让他们全部通过?
任何事情都可以:子类化、委托(delegate)、元编程,但不鼓励后者。
最好将依赖性保持在最低限度:
require 'rspec'
class Foo
# Epic code here
end
describe Foo do
it 'should return an array corresponding to the reverse of the method chain' do
# Why the reverse? So that we're forced to evaluate something
Foo.bar.baz.should == ['baz', 'bar']
Foo.baz.bar.should == ['bar', 'baz']
end
it 'should be able to chain a new method after initial evaluation' do
foobar = Foo.bar
foobar.baz.should == ['baz', 'bar']
foobaz = Foo.baz
foobaz.bar.should == ['bar', 'baz']
end
it 'should not mutate instance data on method calls' do
foobar = Foo.bar
foobar.baz
foobar.baz.should == ['baz', 'bar']
end
it 'should behave as an array as much as possible' do
Foo.bar.baz.map(&:upcase).should == ['BAZ', 'BAR']
Foo.baz.bar.join.should == 'barbaz'
Foo.bar.baz.inject do |acc, str|
acc << acc << str
end.should == 'bazbazbar'
# === There will be cake! ===
# Foo.ancestors.should include Array
# Foo.new.should == []
# Foo.new.methods.should_not include 'method_missing'
end
it "should be a general solution to the problem I'm hoping to solve" do
Foo.bar.baz.quux.rab.zab.xuuq.should == ['xuuq', 'zab', 'rab', 'quux', 'baz', 'bar']
Foo.xuuq.zab.rab.quux.baz.bar.should == ['bar', 'baz', 'quux', 'rab', 'zab', 'xuuq']
foobarbaz = Foo.bar.baz
foobarbazquux = foobarbaz.quux
foobarbazquuxxuuq = foobarbazquux.xuuq
foobarbazquuxzab = foobarbazquux.zab
foobarbaz.should == ['baz', 'bar']
foobarbazquux.should == ['quux', 'baz', 'bar']
foobarbazquuxxuuq.should == ['xuuq', 'quux', 'baz', 'bar']
foobarbazquuxzab.should == ['zab', 'quux', 'baz', 'bar']
end
end
最佳答案
这受到 Amadan 的回答的启发,但使用的代码行数更少:
class Foo < Array
def self.method_missing(message, *args)
new 1, message.to_s
end
def method_missing(message, *args)
dup.unshift message.to_s
end
end
关于ruby-on-rails - Ruby 挑战 - 方法链和惰性求值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8632702/