小编Abd*_*lah的帖子

我这样做有什么不同

class T

  def initialize
   self.class.class_eval do
      def test
        return self.class.object_id
     end
   end
  end

end

和

class T

  def initialize
    singleton_class.class_eval do
      def test
        return self.class.object_id
     end
   end
  end

end

谢谢

PS.Tass回答说,在这个例子中,singleton_class将为每个新对象返回一个不同的object_id,因为singleton_class只属于一个Object.但IRB接下来会说明

1.9.2p180 :001 > class T
1.9.2p180 :002?>   
1.9.2p180 :003 >     def initialize
1.9.2p180 :004?>      singleton_class.class_eval do
1.9.2p180 :005 >               def test
1.9.2p180 :006?>                 return self.class.object_id
1.9.2p180 :007?>              end
1.9.2p180 :008?>        end
1.9.2p180 :009?>     end
1.9.2p180 :010?>   
1.9.2p180 :011 >     end
 => nil 
1.9.2p180 :012 > t = T.new …

我正在使用Cloud Storage for Firebase，无法弄清楚如何访问存储文件

根据https://firebase.google.com/docs/storage/web/start官方指南和https://firebase.google.com/docs/storage/web/create-reference，此代码应返回根引用

let admin = require('firebase-admin')
admin.initializeApp({...})
let storageRef = admin.storage().ref()

但这引发了错误

TypeError：admin.storage（...）。ref不是一个函数

package.json

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {...},
  "dependencies": {
    "@google-cloud/storage": "^1.5.1",
    "firebase": "^4.8.0",
    "firebase-admin": "~5.4.2",
    "firebase-functions": "^0.7.1",
    "pdfkit": "^0.8.3",
    "uuid": "^3.1.0"
  },
  "private": true
}

节点-v => v7.7.4

我的最终目标是下载文件或将pdf文件上传到存储。

我几个月来就注意到了这一点，但直到现在我才没有时间处理它。每当我的 CI 服务器自动执行git pull并重新启动 Rails 服务器时，它们schema.rb都会被随机修改。如下例所示，api_name某个表的列被删除。大约三个月前我放弃了这个专栏。与 相同transportation_charges。通常，该文件中的间距会发生变化：请参阅created_at和updated_at。

这尤其令人烦恼，因为在下次运行时，当我的 CI 执行初始操作时git pull，它会抱怨更改schema.rb并停止执行，直到它们被推送或恢复。而且不仅仅是 CI 服务器。我也在其他开发者机器上看到过这种情况。以前有人遇到过这个吗？

diff --git a/db/schema.rb b/db/schema.rb
index 470d3bf..166e3ee 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -883,7 +883,6 @@ ActiveRecord::Schema.define(version: 20170720211740) do

   create_table "ups_package_service_options", force: :cascade do |t|
     t.string   "name"
-    t.string   "api_name"
     t.string   "type"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
@@ -910,9 +909,8 @@ ActiveRecord::Schema.define(version: 20170720211740) do
     t.string   "code"
     t.string   "name"
     t.string …

const puppeteer = require('puppeteer');

const browser = await puppeteer.launch();
const page = await browser.newPage();

这个有效

await page.goto('https://example.com');

这不起作用（没有协议，即 http/https）

await page.goto("www.example.com');

它抛出错误

协议错误 (Page.navigate)：无法导航到无效 URL

为什么它不像我们在 Google Chrome 中打开时那样附加协议？

我使用asciidoctor-pdf将adoc文档转换为pdf，但总是出现“不是已知字体”的错误，在命令行后添加--trace时，错误是

`initialize':  is not a known font. (Prawn::Errors::UnknownFont)
/usr/local/lib/ruby/gems/2.4.0/gems/prawn-2.2.2/lib/prawn/font/afm.rb:53:in `initialize':  is not a known font. (Prawn::Errors::UnknownFont)
from /usr/local/lib/ruby/gems/2.4.0/gems/prawn-2.2.2/lib/prawn/font.rb:301:in `new'
from /usr/local/lib/ruby/gems/2.4.0/gems/prawn-2.2.2/lib/prawn/font.rb:301:in `load'
from /usr/local/lib/ruby/gems/2.4.0/gems/prawn-2.2.2/lib/prawn/font.rb:253:in `find_font'
from /usr/local/lib/ruby/gems/2.4.0/gems/prawn-2.2.2/lib/prawn/font.rb:57:in `font'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/prawn_ext/extensions.rb:196:in `font'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:2930:in `theme_font'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:544:in `convert_admonition'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:118:in `convert'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:70:in `convert'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:79:in `block in content'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:79:in `map'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:79:in `content'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/block.rb:110:in `content'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:134:in `convert_content_for_block'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:479:in `convert_preamble'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-pdf-1.5.0.alpha.16/lib/asciidoctor-pdf/converter.rb:118:in `convert'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:70:in `convert'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:79:in `block in content'
from /usr/local/lib/ruby/gems/2.4.0/gems/asciidoctor-1.5.6.1/lib/asciidoctor/abstract_block.rb:79:in `map'
from …