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Ruby PG gem连接问题(Ruby PG gem connection issue)

 我已经搜索了几个相关的帖子，但我找不到答案。 我是大多数人使用Mac的编码程序的学生，但是我使用的是Windows（7，Pro，64） - 因为我对这里发布的工具/软件有点紧张。  
 我正在尝试通过Ruby打开与pg gem的连接，我正在使用Sinatra和PostgreSQL。 我已经为PostgreSQL建立了服务器，数据库和配置路径变量，并且我已经成功安装了pg gem（在其他一些帖子中没有问题）：  
 gem install pg -- --with-pg-config=C:\Program Files\PostgreSQL\9.5\bin  
 所以问题是，当我启动Sinatra并转到localhost时，我得到一个NoMethodError，未定义的方法为nil：NilClass的方法，否则适用于Mac用户。  
 方法是：  
configure :development do
  set :db_config, { dbname: "news_aggregator_development" }
end

configure :test do
  set :db_config, { dbname: "news_aggregator_test" }
end

def db_connection
  begin
    connection = PG.connect(Sinatra::Application.db_config)
    yield(connection)
  ensure
    connection.close
  end
end

get '/articles' do
  @results = db_connection do |conn|
    conn.exec("SELECT * FROM articles")
  end
  erb :index
end
 
 connection返回nil ，因此close方法返回未定义的方法错误。 我不认为存在语法错误，因为我已经与其他人核实了这一点，我认为它可能与pg的连接错误有关。  
 第一次发布所以请轻松告诉我=）如果我遗漏了任何所需信息，请致歉 - 让我知道更多上下文可能会有所帮助，我会尝试提供它！ 谢谢！ 

I've searched several related posts for the issue I'm having but wasn't able to find an answer. I'm a student in a coding program where most people use Mac, but I'm on Windows ( 7, Pro, 64 ) - because of that I'm a bit locked in to the tools/software I'll post here.  
I'm trying to open a connection through Ruby with the pg gem, and I'm using Sinatra and PostgreSQL. I've established the server, database, and configuration path variables for PostgreSQL, and I've successfully installed pg gem (didn't have an issue there as in some of the other posts) with the line: 
gem install pg -- --with-pg-config=C:\Program Files\PostgreSQL\9.5\bin 
So the problem is that when I boot up Sinatra and go to the localhost, I get a NoMethodError, Undefined Method for nil:NilClass on a method that otherwise works for Mac users.  
The method is: 
configure :development do
  set :db_config, { dbname: "news_aggregator_development" }
end

configure :test do
  set :db_config, { dbname: "news_aggregator_test" }
end

def db_connection
  begin
    connection = PG.connect(Sinatra::Application.db_config)
    yield(connection)
  ensure
    connection.close
  end
end

get '/articles' do
  @results = db_connection do |conn|
    conn.exec("SELECT * FROM articles")
  end
  erb :index
end
 
connection returns nil, and so the close method returns with an undefined method error. I don't think there is a syntax error as I've checked with others regarding this, and I'm thinking it might be related to a connection error with pg.  
First time post so please go easy on me =) Apologies if I've left out any needed information - let me know what more context could be helpful and I will try to provide it! Thank you!

原文：https://stackoverflow.com/questions/39309670

更新时间：2023-10-25 13:10

最满意答案

 我认为这会对你有用。 让我知道。  
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
xmlns:msxml="urn:schemas-microsoft-com:xslt"
exclude-result-prefixes="msxsl">

<xsl:output method="xml" omit-xml-declaration="yes" version="1.0" encoding="UTF-8" />

  <!-- Get the parent id of every member. -->
  <xsl:variable name="parents">
    <xsl:apply-templates select="//Members//Member" mode="parents"/>
  </xsl:variable>

  <xsl:variable name="parentList" select="msxml:node-set($parents)"/>

  <xsl:template match="/">
    <xsl:element name="output">
      <xsl:apply-templates select="node()|@*"/>
    </xsl:element>
  </xsl:template>

  <!-- Process each pattern. -->
  <xsl:template match="Pattern">
    <!-- Get the parent ids of the Members in this pattern.  -->
    <xsl:variable name="patternParentIDs">
      <xsl:copy-of select="$parentList/Member[id = current()/Member/@id]/parentid"/>
    </xsl:variable> 

    <xsl:variable name="patternParentIDList" select="msxml:node-set($patternParentIDs)"/>

    <!-- Get a distinct list of patternParentIDs. -->
    <xsl:variable name="distinctParents">
      <xsl:copy-of select="$patternParentIDList/parentid[not(. = preceding-sibling::parentid)]"/>
    </xsl:variable>

    <xsl:variable name="distinctParentList" select="msxml:node-set($distinctParents)"/>

    <!-- Determine of each parent id has all members included. -->
    <xsl:variable name="allMembers">
      <xsl:for-each select="$distinctParentList/parentid">
        <xsl:variable name="parentid" select="."/>

        <xsl:if test="count($parentList/Member[parentid=$parentid]) != count($patternParentIDList/parentid[.=$parentid])">
          <xsl:value-of select="'false'"/>
        </xsl:if>

      </xsl:for-each>
    </xsl:variable>

    <xsl:choose>
      <xsl:when test="string-length($allMembers)=0">
        <xsl:copy>
          <xsl:for-each select="$distinctParentList/parentid">
            <xsl:element name="Member">
              <xsl:attribute name="id">
                <xsl:value-of select="."/>
              </xsl:attribute>
            </xsl:element>
          </xsl:for-each>
        </xsl:copy>
      </xsl:when>
      <xsl:otherwise>
        <xsl:copy>
          <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>


  <!-- Suppress the Members. -->
  <xsl:template match="Members"/>

  <!-- parents mode.  -->
  <xsl:template match="Member" mode="parents">
    <Member>
      <id>
        <xsl:value-of select="@id"/>
      </id>
      <parentid>
        <xsl:value-of select="../@id"/>
      </parentid>
    </Member>
  </xsl:template>

  <!-- Identity. -->
  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*"/>
    </xsl:copy>
  </xsl:template>  

</xsl:stylesheet>

I think this will work for you. Let me know. 
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
xmlns:msxml="urn:schemas-microsoft-com:xslt"
exclude-result-prefixes="msxsl">

<xsl:output method="xml" omit-xml-declaration="yes" version="1.0" encoding="UTF-8" />

  <!-- Get the parent id of every member. -->
  <xsl:variable name="parents">
    <xsl:apply-templates select="//Members//Member" mode="parents"/>
  </xsl:variable>

  <xsl:variable name="parentList" select="msxml:node-set($parents)"/>

  <xsl:template match="/">
    <xsl:element name="output">
      <xsl:apply-templates select="node()|@*"/>
    </xsl:element>
  </xsl:template>

  <!-- Process each pattern. -->
  <xsl:template match="Pattern">
    <!-- Get the parent ids of the Members in this pattern.  -->
    <xsl:variable name="patternParentIDs">
      <xsl:copy-of select="$parentList/Member[id = current()/Member/@id]/parentid"/>
    </xsl:variable> 

    <xsl:variable name="patternParentIDList" select="msxml:node-set($patternParentIDs)"/>

    <!-- Get a distinct list of patternParentIDs. -->
    <xsl:variable name="distinctParents">
      <xsl:copy-of select="$patternParentIDList/parentid[not(. = preceding-sibling::parentid)]"/>
    </xsl:variable>

    <xsl:variable name="distinctParentList" select="msxml:node-set($distinctParents)"/>

    <!-- Determine of each parent id has all members included. -->
    <xsl:variable name="allMembers">
      <xsl:for-each select="$distinctParentList/parentid">
        <xsl:variable name="parentid" select="."/>

        <xsl:if test="count($parentList/Member[parentid=$parentid]) != count($patternParentIDList/parentid[.=$parentid])">
          <xsl:value-of select="'false'"/>
        </xsl:if>

      </xsl:for-each>
    </xsl:variable>

    <xsl:choose>
      <xsl:when test="string-length($allMembers)=0">
        <xsl:copy>
          <xsl:for-each select="$distinctParentList/parentid">
            <xsl:element name="Member">
              <xsl:attribute name="id">
                <xsl:value-of select="."/>
              </xsl:attribute>
            </xsl:element>
          </xsl:for-each>
        </xsl:copy>
      </xsl:when>
      <xsl:otherwise>
        <xsl:copy>
          <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>


  <!-- Suppress the Members. -->
  <xsl:template match="Members"/>

  <!-- parents mode.  -->
  <xsl:template match="Member" mode="parents">
    <Member>
      <id>
        <xsl:value-of select="@id"/>
      </id>
      <parentid>
        <xsl:value-of select="../@id"/>
      </parentid>
    </Member>
  </xsl:template>

  <!-- Identity. -->
  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*"/>
    </xsl:copy>
  </xsl:template>  

</xsl:stylesheet>

Ruby PG gem连接问题(Ruby PG gem connection issue)

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