如何从需要的“gem_name"中解救出来未安装 gem 时

本文介绍了如何从需要的“gem_name"中解救出来未安装 gem 时的处理方法,对大家解决问题具有一定的参考价值

问题描述

我正在编写一个依赖于特定 gem 的库.我需要 gem 并在我的代码中使用它,只要 gem 安装在用户的机器上,一切都很好.但如果不是呢?!

I'm writing a library that depend on a specific gem. I require the gem and use it in my code and everything is hunky-dory as long as the gem is installed on the user's machine. but what if it is not?!

我认为这很好,因为我可以从 require 命令中解救出来,并在输出中打印一条消息,以通知用户缺少的 gem 并优雅地完成它,但我得到了一个错误!

I thought it's fine cause I can rescue from the require command and print a message to the output to inform the user about the lacking gem and finish it gracefully but I get an error!

你能告诉我应该怎么做或者这段代码有什么问题吗:

Could you tell me how it should be done or what is wrong with this piece of code:

begin 
 require "some_gem"
rescue
 puts "please install some_gem first!" 
end

推荐答案

require 如果无法加载所需的库,则会引发 LoadError 异常.但是,您从不从任何地方的 LoadError 中救援,而是从 StandardError 中救援.

require raises a LoadError exception if it can't load the required library. However, you never rescue from LoadError anywhere, you rescue from StandardError.

如果你想从LoadError中解救,你必须这么说:

If you want to rescue from LoadError, you have to say so:

begin 
  require 'some_gem'
rescue LoadError
  puts 'please install some_gem first!'
end

更好的是,确保您确实打印了 正确 缺少的依赖项:

Even better yet, make sure that you are actually printing the correct missing dependency:

begin 
  require 'some_gem'
rescue LoadError => e
  raise unless e.message =~ /some_gem/
  puts 'please install some_gem first!'
end

(这会重新引发与被救出的完全相同的异常,以防异常实际上是由其他地方的其他缺失库引起的.您不想打印误导性信息,对吧?)

(This re-raises the exact same exception that was rescued from, in case that the exception was actually caused by some other missing library somewhere else. You wouldn't want to print misleading information, right?)

根据库的预期目标受众是什么以及他们是否会被转储到控制台的回溯吓跑,您可能希望在任何情况下重新引发异常,而不是仅仅吞下它:

Depending on what the intended target audience for the library is and whether or not they might be scared away by a backtrace being dumped to their console, you might want to re-raise the exception in any case, instead of just swallowing it:

begin 
  require 'some_gem'
rescue LoadError => e
  puts 'please install some_gem first!' if e.message =~ /some_gem/
  raise
end

或者,您可以跳过 puts 而是引发异常,并将消息设置为您要说的内容:

Or, you could skip the puts and instead raise an exception with the message set to what you want to say:

begin 
  require 'some_gem'
rescue LoadError => e
  raise e.exception('please install some_gem first!') if e.message =~ /some_gem/
  raise
end

除了现在异常在错误的地方引发,因此具有错误的行号和堆栈跟踪,因此具有误导性,但这很容易解决:

Except now the exception is raised in the wrong place and thus has the wrong line number and stacktrace and thus is misleading, but that is easily fixed:

begin 
  require 'some_gem'
rescue LoadError => e
  raise unless e.message =~ /some_gem/
  friendly_ex = e.exception('please install some_gem first!')
  friendly_ex.set_backtrace(e.backtrace)
  raise friendly_ex
end

现在您打印的内容与使用 puts 打印的内容几乎相同,但是您有一个适当的"异常,例如允许更好的调试或允许你的图书馆的消费者来拯救那个异常并以他们的方式处理它,这两者都是不可能的,或者至少很难用你的解决方案来吞下异常.

Now you print pretty much the same thing that you would have printed with the puts, but you have a "proper" exception that for example allows better debugging or allows a consumer of your library to rescue that exception and handle it their way, both of which would have been impossible or at least hard with your solution that just swallows the exception.

这篇关于如何从需要的“gem_name"中解救出来未安装 gem 时的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,WP2

admin_action_{$_REQUEST[‘action’]}

do_action( "admin_action_{$_REQUEST[‘action’]}" )动作钩子::在发送“Action”请求变量时激发。Action Hook: Fires when an ‘action’ request variable is sent.目录锚点:#说明#源码说明(Description)钩子名称的动态部分$_REQUEST['action']引用从GET或POST请求派生的操作。源码(Source)更新版本源码位置使用被使用2.6.0 wp-admin/admin.php:...

日期:2020-09-02 17:44:16 浏览:1127

admin_footer-{$GLOBALS[‘hook_suffix’]}

do_action( "admin_footer-{$GLOBALS[‘hook_suffix’]}", string $hook_suffix )操作挂钩:在默认页脚脚本之后打印脚本或数据。Action Hook: Print scripts or data after the default footer scripts.目录锚点:#说明#参数#源码说明(Description)钩子名的动态部分,$GLOBALS['hook_suffix']引用当前页的全局钩子后缀。参数(Parameters)参数类...

日期:2020-09-02 17:44:20 浏览:1032

customize_save_{$this->id_data[‘base’]}

do_action( "customize_save_{$this->id_data[‘base’]}", WP_Customize_Setting $this )动作钩子::在调用WP_Customize_Setting::save()方法时激发。Action Hook: Fires when the WP_Customize_Setting::save() method is called.目录锚点:#说明#参数#源码说明(Description)钩子名称的动态部分,$this->id_data...

日期:2020-08-15 15:47:24 浏览:775

customize_value_{$this->id_data[‘base’]}

apply_filters( "customize_value_{$this->id_data[‘base’]}", mixed $default )过滤器::过滤未作为主题模式或选项处理的自定义设置值。Filter Hook: Filter a Customize setting value not handled as a theme_mod or option.目录锚点:#说明#参数#源码说明(Description)钩子名称的动态部分,$this->id_date['base'],指的是设置...

日期:2020-08-15 15:47:24 浏览:866

get_comment_author_url

过滤钩子:过滤评论作者的URL。Filter Hook: Filters the comment author’s URL.目录锚点:#源码源码(Source)更新版本源码位置使用被使用 wp-includes/comment-template.php:32610...

日期:2020-08-10 23:06:14 浏览:903

network_admin_edit_{$_GET[‘action’]}

do_action( "network_admin_edit_{$_GET[‘action’]}" )操作挂钩:启动请求的处理程序操作。Action Hook: Fires the requested handler action.目录锚点:#说明#源码说明(Description)钩子名称的动态部分$u GET['action']引用请求的操作的名称。源码(Source)更新版本源码位置使用被使用3.1.0 wp-admin/network/edit.php:3600...

日期:2020-08-02 09:56:09 浏览:848

network_sites_updated_message_{$_GET[‘updated’]}

apply_filters( "network_sites_updated_message_{$_GET[‘updated’]}", string $msg )筛选器挂钩:在网络管理中筛选特定的非默认站点更新消息。Filter Hook: Filters a specific, non-default site-updated message in the Network admin.目录锚点:#说明#参数#源码说明(Description)钩子名称的动态部分$_GET['updated']引用了非默认的...

日期:2020-08-02 09:56:03 浏览:834

pre_wp_is_site_initialized

过滤器::过滤在访问数据库之前是否初始化站点的检查。Filter Hook: Filters the check for whether a site is initialized before the database is accessed.目录锚点:#源码源码(Source)更新版本源码位置使用被使用 wp-includes/ms-site.php:93910...

日期:2020-07-29 10:15:38 浏览:809

WordPress 的SEO 教学:如何在网站中加入关键字(Meta Keywords)与Meta 描述(Meta Description)?

你想在WordPress 中添加关键字和meta 描述吗?关键字和meta 描述使你能够提高网站的SEO。在本文中,我们将向你展示如何在WordPress 中正确添加关键字和meta 描述。为什么要在WordPress 中添加关键字和Meta 描述?关键字和说明让搜寻引擎更了解您的帖子和页面的内容。关键词是人们寻找您发布的内容时,可能会搜索的重要词语或片语。而Meta Description则是对你的页面和文章的简要描述。如果你想要了解更多关于中继标签的资讯,可以参考Google的说明。Meta 关键字和描...

日期:2020-10-03 21:18:25 浏览:1619

谷歌的SEO是什么

SEO (Search Engine Optimization)中文是搜寻引擎最佳化,意思近于「关键字自然排序」、「网站排名优化」。简言之,SEO是以搜索引擎(如Google、Bing)为曝光媒体的行销手法。例如搜寻「wordpress教学」,会看到本站的「WordPress教学:12个课程…」排行Google第一:关键字:wordpress教学、wordpress课程…若搜寻「网站架设」,则会看到另一个网页排名第1:关键字:网站架设、架站…以上两个网页,每月从搜寻引擎导入自然流量,达2万4千:每月「有机搜...

日期:2020-10-30 17:23:57 浏览:1263