ruby-on-rails - 如何在 jbuilder 视图中返回空字符串而不是 null？

Question

我有简单的 jbuilder 视图

json.id pharmaceutic.id
json.name pharmaceutic.name
json.dosage pharmaceutic.dosage.name

什么时候pharmaceutic.dosage => nil

我渲染的 json 如下所示：

{"id":1,"name":"HerzASS ratiopharm","dosage":null}

我想为所有 jBuilder 视图设置，当某个属性存在时，nil它应该呈现为空字符串。

{"id":1,"name":"HerzASS ratiopharm","dosage":""}

如何做到这一点？

Answer 1

nil.to_s #=> ""所以，你可以简单地添加.to_s

json.id pharmaceutic.id
json.name pharmaceutic.name.to_s
json.dosage pharmaceutic.dosage.name.to_s

Answer 2

为了扩展接受的答案，这里有一个简单的代理类来做到这一点：

class Proxy

  def initialize(object)
    @object = object
  end

  def method_missing method, *args, &block
    if @object.respond_to? method
      @object.send(method, *args, &block).to_s
    else
      super method, *args, &block
    end
  end

  def respond_to? method, private = false
    super(method, private) || @object.respond_to?(method, private)
  end

end

class Roko < Struct.new(:a, :b, :c)
end

# instantiate the proxy instance by giving it the reference to the object in which you don't want nils
roko = Proxy.new(Roko.new)

puts roko.a.class # returns String even though :a is uninitialized
puts roko.a       # returns blank

Answer 3

json.dosage pharmaceutic.dosage.name.to_s

如果 pharmaceutic 为 nil，这将不起作用。你可以简单地做

json.dosage pharmaceutic.dosage.name unless pharmaceutic.dosage.nil?