ruby - ruby 中的条件链接

Question

我已阅读 this question ，但我无法创建完整示例:

class Some
  def method_a
    puts "a"
  end

  def method_b
    puts "b"
  end

  def method_c
    puts "c"
  end
end

some = Some.new

a = true
b = true
c = true

l = []
l << :method_a if a
l << :method_b if b
l << :method_c if c

l.inject(some) { |obj, method|
  obj.send(method)
}

[demas @arch.local.net ][~/dev/study/ruby/oop]% ruby inject_ex.rb
a

inject_ex.rb:26:in block in <main>': undefined method method_b' for nil:NilClass

(NoMethodError)

from inject_ex.rb:26:in `each'

from inject_ex.rb:26:in `inject'

from inject_ex.rb:26:in `'

Answer 1

Inject 将 block 的返回值传递给下一次迭代。现在，您的 obj 在第一次迭代后具有 obj.send(:method_a) 的返回值。像这样修复你的注入(inject):

l.inject(some) { |obj, method|
  obj.send(method)
  obj
}