單引號(hào)內(nèi)的內(nèi)容,ruby會(huì)原樣輸出

雙引號(hào)內(nèi)的內(nèi)容,ruby會(huì)解析

我們看個(gè)簡單的例子,針對(duì)字符串 ? ???#{foo}test? ? ?我們分別用單引號(hào)核雙引號(hào)操作

'#{foo}test' => "\#{foo}test"

　　

"#{foo}test" NameError: undefined local variable or?method `foo' for?main:Object ????????from (irb):4 ????????from C:/Ruby192/bin/irb:12:in?`<main>'

顯而易見, 雙引號(hào)對(duì)字符串內(nèi)的#進(jìn)行了解析, 導(dǎo)致ruby認(rèn)為foo是個(gè)方法,出錯(cuò).

類似的, %W %Q 相當(dāng)于雙引號(hào), ? %w %q 相當(dāng)于單引號(hào).

?

轉(zhuǎn)載:?http://simpleror.wordpress.com/2009/03/15/q-q-w-w-x-r-s/??

%Q

This is an alternative for double-quoted strings, when you have more quote characters in a string.Instead of putting backslashes in front of them, you can easily write:
>> %Q(Joe said: "Frank said: "#{what_frank_said}"")
=> "Joe said: "Frank said: "Hello!"""

The parenthesis “(…)” can be replaced with any other non-alphanumeric characters and non-printing characters (pairs), so the following commands are equivalent:
>> %Q!Joe said: "Frank said: "#{what_frank_said}""!
>> %Q[Joe said: "Frank said: "#{what_frank_said}""]
>> %Q+Joe said: "Frank said: "#{what_frank_said}""+

You can use also:
>> %/Joe said: "Frank said: "#{what_frank_said}""/
=> "Joe said: "Frank said: "Hello!"""

?

%q

Used for single-quoted strings.The syntax is similar to?%Q, but single-quoted strings are not subject to expression substitution or escape sequences.
>> %q(Joe said: 'Frank said: '#{what_frank_said} ' ')
=> "Joe said: 'Frank said: '\#{what_frank_said} ' '"

?

%W

Used for double-quoted array elements.The syntax is similar to?%Q
>> %W(#{foo} Bar Bar\ with\ space)
=> ["Foo", "Bar", "Bar with space"]

?

%w

Used for single-quoted array elements.The syntax is similar to?%Q, but single-quoted elements are not subject to expression substitution or escape sequences.
>> %w(#{foo} Bar Bar\ with\ space)
=> ["\#{foo}", "Bar", "Bar with space"]

?

%x

Uses the?`?method and returns the standard output of running the command in a subshell.The syntax is similar to?%Q.
>> %x(echo foo:#{foo})
=> "foo:Foo\n"

?

%r

Used for regular expressions.The syntax is similar to?%Q.
>> %r(/home/#{foo})
=> "/\\/home\\/Foo/"

?

%s

Used for symbols.It’s not subject to expression substitution or escape sequences.
>> %s(foo)
=> :foo
>> %s(foo bar)
=> :"foo bar"
>> %s(#{foo} bar)
=> :"\#{foo} bar"

轉(zhuǎn)載于:https://www.cnblogs.com/buhaiqing/p/3537558.html

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