blocks|key|923154|text|据我所知，恐怕没什么可做的。我通常这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|923155|def+distinct_count
++++<<-EOF.gsub+/%5E\s%2B/,+""
++++++++\tSELECT
++++++++\t+CAST('#{name}'+AS+VARCHAR(30))+as+COLUMN_NAME
++++++++\t,COUNT(DISTINCT+#{name})+AS+DISTINCT_COUNT
++++++++\tFROM+#{table.call}
++++EOF
end|code-block|syntax|javascript|923156|这是可行的，但有点小麻烦。|923157|编辑:从下面的Rene+Saarsoo获得灵感，我建议这样做：|923158|class+String
++def+unindent+
++++gsub(/%5E#{scan(/%5E\s*/).min_by{%7Cl%7Cl.length}}/,+"")
++end
end

def+distinct_count
++++<<-EOF.unindent
++++++++\tSELECT
++++++++\t+CAST('#{name}'+AS+VARCHAR(30))+as+COLUMN_NAME
++++++++\t,COUNT(DISTINCT+#{name})+AS+DISTINCT_COUNT
++++++++\tFROM+#{table.call}
++++EOF
end|923159|当第一行也不是最左边的那一行时，这个版本应该会处理。|923160|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Not much to do that I know of I'm afraid. I usually do:

<pre><code>def distinct_count
 &lt;&lt;-EOF.gsub /^\s+/, ""
 \tSELECT
 \t CAST('#{name}' AS VARCHAR(30)) as COLUMN_NAME
 \t,COUNT(DISTINCT #{name}) AS DISTINCT_COUNT
 \tFROM #{table.call}
 EOF
end
</code></pre>

That works but is a bit of a hack.

EDIT:
Taking inspiration from Rene Saarsoo below, I'd suggest something like this instead:

<pre><code>class String
 def unindent 
 gsub(/^#{scan(/^\s*/).min_by{|l|l.length}}/, "")
 end
end

def distinct_count
 &lt;&lt;-EOF.unindent
 \tSELECT
 \t CAST('#{name}' AS VARCHAR(30)) as COLUMN_NAME
 \t,COUNT(DISTINCT #{name}) AS DISTINCT_COUNT
 \tFROM #{table.call}
 EOF
end
</code></pre>

This version should handle when the first line is not the one farthest to the left too.

blocks|key|1137708|text|Ruby中的<<-将只忽略结束分隔符的前导空格，从而允许它被适当地缩进。它不会去掉字符串内部行上的前导空格，尽管一些在线文档可能会这样说。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1137709|您可以使用gsub自己删除前导空格|1137710|<<-EOF.gsub+/%5E\s*/,+''
++++\tSELECT
++++\t+CAST('#{name}'+AS+VARCHAR(30))+as+COLUMN_NAME
++++\t,COUNT(DISTINCT+#{name})+AS+DISTINCT_COUNT
++++\tFROM+#{table.call}
EOF|code-block|syntax|javascript|1137711|或者，如果您只想删除空格，留下制表符：|1137712|<<-EOF.gsub+/%5E+*/,+''
++++\tSELECT
++++\t+CAST('#{name}'+AS+VARCHAR(30))+as+COLUMN_NAME
++++\t,COUNT(DISTINCT+#{name})+AS+DISTINCT_COUNT
++++\tFROM+#{table.call}
EOF|1137713|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core/classes/String.html#M001186^0|6|3|0|5|4|5|4|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|18|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

<code>&lt;&lt;-</code> in Ruby will only ignore leading space for the ending delimiter, allowing it to be properly indented. It does not strip leading space on lines inside the string, despite what some documentation online might say.

You can strip leading whitespace yourself by using <a href="http://ruby-doc.org/core/classes/String.html#M001186" rel="noreferrer"><code>gsub</code></a>:

<pre><code>&lt;&lt;-EOF.gsub /^\s*/, ''
 \tSELECT
 \t CAST('#{name}' AS VARCHAR(30)) as COLUMN_NAME
 \t,COUNT(DISTINCT #{name}) AS DISTINCT_COUNT
 \tFROM #{table.call}
EOF
</code></pre>

Or if you just want to strip spaces, leaving the tabs:

<pre><code>&lt;&lt;-EOF.gsub /^ */, ''
 \tSELECT
 \t CAST('#{name}' AS VARCHAR(30)) as COLUMN_NAME
 \t,COUNT(DISTINCT #{name}) AS DISTINCT_COUNT
 \tFROM #{table.call}
EOF
</code></pre>

blocks|key|923258|text|就像最初的帖子一样，我也发现了<<-HEREDOC语法，并且对它没有按照我所认为的方式运行感到非常失望。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|923259|但是我没有在代码中使用gsub-s，而是扩展了String类：|923260|class+String
++#+Removes+beginning-whitespace+from+each+line+of+a+string.
++#+But+only+as+many+whitespace+as+the+first+line+has.
++#
++#+Ment+to+be+used+with+heredoc+strings+like+so:
++#
++#+text+=+<<-EOS.unindent
++#+++This+line+has+no+indentation
++#+++++This+line+has+2+spaces+of+indentation
++#+++This+line+is+also+not+indented
++#+EOS
++#
++def+unindent
++++lines+=+[]
++++each_line+{%7Cln%7C+lines+<<+ln+}

++++first_line_ws+=+lines[0].match(/%5E\s%2B/)[0]
++++re+=+Regexp.new('%5E\s{0,'+%2B+first_line_ws.length.to_s+%2B+'}')

++++lines.collect+{%7Cline%7C+line.sub(re,+"")+}.join
++end
end|code-block|syntax|javascript|923261|entityMap^0|F|A|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Like the original poster, I too discovered the <code>&lt;&lt;-HEREDOC</code> syntax and was pretty damn disappointed that it didn't behave as I thought it should behave.

But instead of littering my code with gsub-s I extended the String class:

<pre><code>class String
 # Removes beginning-whitespace from each line of a string.
 # But only as many whitespace as the first line has.
 #
 # Ment to be used with heredoc strings like so:
 #
 # text = &lt;&lt;-EOS.unindent
 # This line has no indentation
 # This line has 2 spaces of indentation
 # This line is also not indented
 # EOS
 #
 def unindent
 lines = []
 each_line {|ln| lines &lt;&lt; ln }

 first_line_ws = lines[0].match(/^\s+/)[0]
 re = Regexp.new('^\s{0,' + first_line_ws.length.to_s + '}')

 lines.collect {|line| line.sub(re, "") }.join
 end
end
</code></pre>

blocks|key|1137829|text|如果您使用的是Rails3.0或更新版本，请尝试#strip_heredoc。This+example+from+the+docs打印前三行时没有缩进，而最后两行保留了两个空格的缩进：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1137830|if+options[:usage]
  puts+<<-USAGE.strip_heredoc
    This+command+does+such+and+such.
 
    Supported+options+are:
      -h        +This+message
      ...
  USAGE
end|code-block|syntax|javascript|1137831|文档还指出：“从技术上讲，它会在整个字符串中查找缩进最少的行，并删除前导空格。”|1137832|下面是来自active_support/core_ext/string/strip.rb的实现|1137833|class+String
++def+strip_heredoc
++++indent+=+scan(/%5E[+\t]*(?=\S)/).min.try(:size)+%7C%7C+0
++++gsub(/%5E[+\t]{#{indent}}/,+'')
++end
end|1137834|您可以在test/core_ext/string_ext_test.rb中找到这些测试。|1137835|entityMap|0|LINK|mutability|MUTABLE|url|http://guides.rubyonrails.org/active_support_core_extensions.html#strip-heredoc|1|https://github.com/rails/rails/blob/b422cda2ebfff4032f4c18271e96ad329c413dcc/activesupport/lib/active_support/core_ext/string/strip.rb|2|https://github.com/rails/rails/blob/b422cda2ebfff4032f4c18271e96ad329c413dcc/activesupport/test/core_ext/string_ext_test.rb#L14-43^0|O|E|13|Q|0|0|0|0|5|13|1|0|0|4|W|2|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1B|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|1C|8|@]|D|@$9|1D|A|1E|1|1F]]|E|$]]|$1|O|3|P|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|1H|8|@]|D|@$9|1I|A|1J|1|1K]]|E|$]]|$1|S|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]|12|$5|V|W|X|E|$Y|13]]]]

If you're using Rails 3.0 or newer, try <code>#strip_heredoc</code>. <a href="http://guides.rubyonrails.org/active_support_core_extensions.html#strip-heredoc">This example from the docs</a> prints the first three lines with no indentation, while retaining the last two lines' two-space indentation:

<pre class="lang-ruby prettyprint-override"><code>if options[:usage]
  puts &lt;&lt;-USAGE.strip_heredoc
    This command does such and such.
 
    Supported options are:
      -h         This message
      ...
  USAGE
end
</code></pre>

The documentation also notes: "Technically, it looks for the least indented line in the whole string, and removes that amount of leading whitespace."

Here's the implementation from <a href="https://github.com/rails/rails/blob/b422cda2ebfff4032f4c18271e96ad329c413dcc/activesupport/lib/active_support/core_ext/string/strip.rb">active_support/core_ext/string/strip.rb</a>:

<pre class="lang-ruby prettyprint-override"><code>class String
 def strip_heredoc
 indent = scan(/^[ \t]*(?=\S)/).min.try(:size) || 0
 gsub(/^[ \t]{#{indent}}/, '')
 end
end
</code></pre>

And you can find the tests in <a href="https://github.com/rails/rails/blob/b422cda2ebfff4032f4c18271e96ad329c413dcc/activesupport/test/core_ext/string_ext_test.rb#L14-43">test/core_ext/string_ext_test.rb</a>.

blocks|key|1137898|text|另一个容易记住的选项是使用unindent+gem|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1137899|require+'unindent'

p+<<-end.unindent
++++hello
++++++world
++end
#+=>+"hello\n++world\n"++|code-block|syntax|javascript|1137900|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

another easy to remember option is to use unindent gem

<pre><code>require 'unindent'

p &lt;&lt;-end.unindent
 hello
 world
 end
# =&gt; "hello\n world\n" 
</code></pre>

blocks|key|1137948|text|我收集答案并得到以下结果：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1137949|class+Match+<+ActiveRecord::Base
++has_one+:invitation
++scope+:upcoming,+->+do
++++joins(:invitation)
++++.where(<<-SQL_QUERY.strip_heredoc,+Date.current,+Date.current).order('invitations.date+ASC')
++++++CASE+WHEN+invitations.autogenerated_for_round+IS+NULL+THEN+invitations.date+>=+?
++++++ELSE+(invitations.round_end_time+>=+?+AND+match_plays.winner_id+IS+NULL)+END
++++SQL_QUERY
++end
end|code-block|syntax|javascript|1137950|它可以生成出色的SQL，并且不会超出AR范围。|1137951|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I collect answers and got this:

<pre><code>class Match &lt; ActiveRecord::Base
 has_one :invitation
 scope :upcoming, -&gt; do
 joins(:invitation)
 .where(&lt;&lt;-SQL_QUERY.strip_heredoc, Date.current, Date.current).order('invitations.date ASC')
 CASE WHEN invitations.autogenerated_for_round IS NULL THEN invitations.date &gt;= ?
 ELSE (invitations.round_end_time &gt;= ? AND match_plays.winner_id IS NULL) END
 SQL_QUERY
 end
end
</code></pre>

It generates excellent SQL and do not go out of AR scopes.

blocks|key|923478|text|我需要在system中使用一些东西，这样我就可以将长的sed命令分成几行，然后删除缩进和换行符……|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|923479|def+update_makefile(build_path,+version,+sha1)
++system+<<-CMD.strip_heredoc(true)
++++\\sed+-i".bak"
++++-e+"s/GIT_VERSION[\+]*:=.*/GIT_VERSION+:=+20171-2342/g"
++++-e+"s/GIT_VERSION_SHA1[\+]:=.*/GIT_VERSION_SHA1+:=+2342/g"
++++"/tmp/Makefile"
++CMD
end|code-block|syntax|javascript|923480|所以我想出了这个：|923481|class+::String
++def+strip_heredoc(compress+=+false)
++++stripped+=+gsub(/%5E#{scan(/%5E\s*/).min_by(&:length)}/,+"")
++++compress+?+stripped.gsub(/\n/,"+").chop+:+stripped
++end
end|923482|默认行为是不删除换行符，就像所有其他示例一样。|923483|entityMap^0|4|6|R|3|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

I needed to use something with <code>system</code> whereby I could split long <code>sed</code> commands across lines and then remove indentation AND newlines...

<pre><code>def update_makefile(build_path, version, sha1)
 system &lt;&lt;-CMD.strip_heredoc(true)
 \\sed -i".bak"
 -e "s/GIT_VERSION[\ ]*:=.*/GIT_VERSION := 20171-2342/g"
 -e "s/GIT_VERSION_SHA1[\ ]:=.*/GIT_VERSION_SHA1 := 2342/g"
 "/tmp/Makefile"
 CMD
end
</code></pre>

So I came up with this:

<pre><code>class ::String
 def strip_heredoc(compress = false)
 stripped = gsub(/^#{scan(/^\s*/).min_by(&amp;:length)}/, "")
 compress ? stripped.gsub(/\n/," ").chop : stripped
 end
end
</code></pre>

Default behavior is to not strip newlines, just like all the other examples.

I'm having a problem with a Ruby heredoc i'm trying to make. It's returning the leading whitespace from each line even though i'm including the - operator, which is supposed to suppress all leading whitespace characters. my method looks like this:

<pre><code> def distinct_count
 &lt;&lt;-EOF
 \tSELECT
 \t CAST('#{name}' AS VARCHAR(30)) as COLUMN_NAME
 \t,COUNT(DISTINCT #{name}) AS DISTINCT_COUNT
 \tFROM #{table.call}
 EOF
end
</code></pre>

and my output looks like this:

<pre><code> =&gt; " \tSELECT\n \t CAST('SRC_ACCT_NUM' AS VARCHAR(30)) as
COLUMN_NAME\n \t,COUNT(DISTINCT SRC_ACCT_NUM) AS DISTINCT_COUNT\n
 \tFROM UD461.MGMT_REPORT_HNB\n"
</code></pre>

this, of course, is right in this specific instance, except for all the spaces between the first " and \t. does anyone know what i'm doing wrong here?

How do I remove leading whitespace chars from Ruby HEREDOC?

我想做的Ruby heredoc出了点问题。它返回每一行的前导空格，即使我包含了-运算符，它应该隐藏所有前导空格字符。我的方法看起来像这样： def distinct_count <<-EOF \tSELECT \t CAST('#{name}' AS VARCHAR(30)) ...

问如何从Ruby HEREDOC中删除前导空格字符？
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