Rubyonrails 为什么是 json.partial！使用新的哈希语法传递本地时，jbuiler 模板中的行不执行

发布于04月19日

我在我的jBuilder模板中使用了新的散列语法.看来这一行根本没有执行.

json.partial! 'comments', post:, comments:

如果我将该行修改回旧语法，或者添加大括号或方括号，它就会起作用.

json.partial!('comments', post:, comments:)
json.partial! 'comments', { post:, comments: }
json.partial! 'comments', post: post, comments: comments

有人能解释一下这里发生了什么吗？是不是跟模板编译有关？谢谢.

推荐答案

为简单起见，测试模板:

# app/views/test.json.jbuilder
json.attr name:

我不知道如何通过其他方式访问它，但您可以在以下位置查看编译后的source: 一百零二

要查看模板呈现时实际运行的代码，请执行以下操作:

>> ApplicationController.renderer.render(template: "test", locals: {name: "first"})
  Rendering test.json.jbuilder
"          def _app_views_test_json_jbuilder__1585277848127427767_29960(local_assigns, output_buffer)\n            @virtual_path = \"test\";name = local_assigns[:name]; name = name;;__already_defined = defined?(json); json||=JbuilderTemplate.new(self); json.attr name:\n\n      json.target! unless (__already_defined && __already_defined != \"method\")\n          end\n"
=> TypeError # doesn't actually render

formatted个

def _app_views_test_json_jbuilder__1161877154070863274_90100(local_assigns, output_buffer)
  @virtual_path = "test";               # ActionView
  name = local_assigns[:name];          # ActionView
  name = name;;                         # ActionView
  __already_defined = defined?(json);   # Jbuilder
  json||=JbuilderTemplate.new(self);    # Jbuilder
  json.attr name:                       # Your template
  json.target! unless (__already_defined && __already_defined != "method")
  #    ^ Jbuilder json output
end

如果您没有用括号括起来，则json.target!将成为name的值，并且您的模板将返回json.attr返回的值或您的模板返回的json.partial!.

It's also fixable if you put a semicolon at the end of this line:
https://github.com/rails/jbuilder/blob/v2.11.5/lib/jbuilder/jbuilder_template.rb#L277

#                                                                            here v
%{__already_defined = defined?(json); json||=JbuilderTemplate.new(self); #{source};

>> ApplicationController.renderer.render(template: "test", locals: {name: "first"})
=> "{\"attr\":{\"name\":\"first\"}}"

简化版

def json *args
  @buffer = [*@buffer, *args]
end

def target 
  @buffer&.join
ensure
  @buffer = nil
end

# ^ this is action view/jbuilder
# v this is jbuilder templates

def good_template name = "first"
  json(name:)
  target
end

# same as doing:
# `json name: target`
def bad_template name = "first"
  json name:
  target
end

>> good_template
=> "{:name=>\"first\"}"
>> bad_template
=> [{:name=>nil}]       # Array instead of a String, if we had a controller
                        # there would be a TypeError somewhere.

So method hash: is still an iffy syntax and much less obvious in a template. Just use parenthesis:
https://bugs.ruby-lang.org/issues/18396