blocks|key|1356470|text|这是运算符优先级的问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1356471|%7C%7C比or具有更高的优先级。|offset|length|style|CODE|1356472|因此，在这两者之间还有其他运算符，包括三元运算符(?+:)和赋值运算符(=)，因此您选择哪个运算符可以影响语句的结果。|1356473|这是一个ruby+operator+precedence+table。|1356474|有关使用and/&&的另一个示例，请参阅this+question。|1356475|另外，要注意可能会发生的一些糟糕的事情：|1356476|a+=+false+%7C%7C+true++#=>+true
a++#=>+true

a+=+false+or+true++#=>+true
a++#=>+false|code-block|syntax|javascript|1356477|前两个语句的计算结果都是true，但第二个语句将a设置为false，因为=优先级低于%7C%7C但高于or。|1356478|entityMap|0|LINK|mutability|MUTABLE|url|http://phrogz.net/programmingruby/language.html#table_18.4|1|https://stackoverflow.com/questions/1840488/ruby-operator-precedence-and^0|0|0|2|3|2|0|P|3|10|1|0|4|U|0|0|4|3|8|2|K|D|1|0|0|0|C|4|O|1|S|5|10|1|16|2|1B|2|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@$D|18|E|19|F|G]|$D|1A|E|1B|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1C|8|@$D|1D|E|1E|F|G]|$D|1F|E|1G|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1H|8|@]|9|@$D|1I|E|1J|1|1K]]|A|$]]|$1|L|3|M|5|6|7|1L|8|@$D|1M|E|1N|F|G]|$D|1O|E|1P|F|G]]|9|@$D|1Q|E|1R|1|1S]]|A|$]]|$1|N|3|O|5|6|7|1T|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|1U|8|@]|9|@]|A|$S|T]]|$1|U|3|V|5|6|7|1V|8|@$D|1W|E|1X|F|G]|$D|1Y|E|1Z|F|G]|$D|20|E|21|F|G]|$D|22|E|23|F|G]|$D|24|E|25|F|G]|$D|26|E|27|F|G]]|9|@]|A|$]]|$1|W|3|-4|5|6|7|28|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]|14|$5|Z|10|11|A|$12|15]]]]

It's a matter of operator precedence.

<code>||</code> has a higher precedence than <code>or</code>.

So, in between the two you have other operators including ternary (<code>? :</code>) and assignment (<code>=</code>) so which one you choose can affect the outcome of statements.

Here's a <a href="http://phrogz.net/programmingruby/language.html#table_18.4" rel="noreferrer">ruby operator precedence table</a>.

See <a href="https://stackoverflow.com/questions/1840488/ruby-operator-precedence-and">this question</a> for another example using <code>and</code>/<code>&amp;&amp;</code>.

Also, be aware of some nasty things that could happen: 

<pre><code>a = false || true #=&gt; true
a #=&gt; true

a = false or true #=&gt; true
a #=&gt; false
</code></pre>

Both of the previous two statements evaluate to <code>true</code>, but the second sets <code>a</code> to <code>false</code> since <code>=</code> precedence is lower than <code>||</code> but higher than <code>or</code>.

blocks|key|1356516|text|补充一下mopoke的答案，这也是一个语义问题。or被认为是一种很好的实践，因为它读起来比%7C%7C好得多。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1356517|entityMap^0|O|2|19|2|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Just to add to mopoke's answer, it's also a matter of semantics. <code>or</code> is considered to be a good practice because it reads much better than <code>||</code>.

blocks|key|1356606|text|如果任一操作数为true，则or和%7C%7C的计算结果均为true。只有当第一个操作数为false时，它们才会计算第二个操作数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1356607|与and一样，or和%7C%7C之间的唯一区别是它们的优先级。|1356608|为了让生活更有趣，and和or具有相同的优先级，而&&的优先级比%7C%7C更高。|1356609|entityMap^0|E|2|H|2|0|1|3|7|2|A|2|0|9|3|D|2|P|2|W|2|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|K|$]]

Both <code>or</code> and <code>||</code> evaluate to true if either operand is true. They evaluate their second operand only if the first is false. 

As with <code>and</code>, the only difference between <code>or</code> and <code>||</code> is their precedence.

Just to make life interesting, <code>and</code> and <code>or</code> have the same precedence, while <code>&amp;&amp;</code> has a higher precedence than <code>||</code>.

blocks|key|1356637|text|and/or是用于控制流的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1356638|Ruby不允许将其作为有效语法：|1356639|false+%7C%7C+raise+"Error"|code-block|syntax|javascript|1356640|然而，这是有效的：|1356641|false+or+raise+"Error"|1356642|您可以使用()实现第一种方法，但使用or是正确的方法。|1356643|false+%7C%7C+(raise+"Error")|1356644|entityMap^0|0|3|4|2|0|0|0|0|0|5|2|I|2|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|12|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|13|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|14|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@]|E|$]]|$1|S|3|T|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|U|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|V|$]]

<code>and</code>/<code>or</code> are for control flow. 

Ruby will not allow this as valid syntax:

<pre><code>false || raise "Error"
</code></pre>

However this is valid:

<pre><code>false or raise "Error"
</code></pre>

You can make the first work, with <code>()</code> but using <code>or</code> is the correct method.

<pre><code>false || (raise "Error")
</code></pre>

blocks|key|1356712|text|我使用这些运算符的方式如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1356713|%7C%7C,+&&用于布尔逻辑。or,+and用于控制流。例如。|offset|length|style|CODE|1356714|do_smth+if+may_be+%7C%7C+may_be+--我们在这里评估条件|1356715|do_smth+or+do_smth_else+--我们定义工作流，它等同于do_smth_else+unless+do_smth|1356716|举个简单的例子：|1356717|>+puts+"a"+&&+"b"
b

>+puts+'a'+and+'b'
a|code-block|syntax|javascript|1356718|Rails中的一个众所周知的习惯用法是render+and+return。这是说return+if+render的快捷方式，而render+&&+return不起作用。有关更多信息，请参阅Rails文档中的"Avoiding+Double+Render+Errors“。|1356719|entityMap|0|LINK|mutability|MUTABLE|url|http://guides.rubyonrails.org/layouts_and_rendering.html#avoiding-double-render-errors^0|0|0|6|D|7|0|0|R|0|0|N|12|R|0|0|0|J|H|14|G|1R|G|2W|T|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]|$D|16|E|17|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|18|8|@$D|19|E|1A|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1B|8|@$D|1C|E|1D|F|G]|$D|1E|E|1F|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1G|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1H|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1I|8|@$D|1J|E|1K|F|G]|$D|1L|E|1M|F|G]|$D|1N|E|1O|F|G]]|9|@$D|1P|E|1Q|1|1R]]|A|$]]|$1|U|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

The way I use these operators: 

<code>||, &amp;&amp;</code> are for boolean logic. <code>or, and</code> are for control flow. E.g.

<code>do_smth if may_be || may_be</code> -- we evaluate the condition here

<code>do_smth or do_smth_else</code> -- we define the workflow, which is equivalent to
<code>do_smth_else unless do_smth</code>

to give a simple example:

<pre><code>&gt; puts "a" &amp;&amp; "b"
b

&gt; puts 'a' and 'b'
a
</code></pre>

A well-known idiom in Rails is <code>render and return</code>. It's a shortcut for saying <code>return if render</code>, while <code>render &amp;&amp; return</code> won't work. See "<a href="http://guides.rubyonrails.org/layouts_and_rendering.html#avoiding-double-render-errors" rel="nofollow noreferrer">Avoiding Double Render Errors</a>" in the Rails documentation for more information.

What's the difference between the <code>or</code> and <code>||</code> operators in Ruby? Or is it just preference?

Difference between "or" and || in Ruby?

Ruby语言

Ruby语言中的or和||操作符有什么不同？或者这只是一个偏好？

问Ruby中"or“和||的区别是什么？
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