Ruby 价值或；“违约”；

可能重复：

我用Lua

x = value or "default_if_value_is_nil"

（作为

的快捷方式，如果value~=nil，则x=value end

）

我可以用Ruby做类似的事情吗

x = value || "default_if_value_is_nil_or_false"

---

注意这里的“or false”，虽然Lua中可能也有相同的情况。

您实际上可以在ruby中做同样的事情

x = nil_value || "default"

请注意，这也适用于任何其他“虚假”值

x = false_value || "default"

是一个完全合法的Ruby语句，但请注意，

或

在运算符优先级中具有最低优先级之一。还要知道，在Ruby布尔运算中，除了false和nil之外，所有的东西都是true，因此，即使值不是nil而是false，这个Ruby语句也会回答缺省值

puts '>>> assignment = has a higher priority than or <<<'
value = 'y'
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

puts '>>> put parenthesis around or expression to have a higher priority than = <<<'
value = 'y'
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

puts '>>> || has a higher priority than = <<<'
value = 'y'
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

---

put'>>>assignment=的优先级高于，或者将括号括起来，或者表达式的优先级高于=| |的优先级高于=哇，这很简单。那么| |和或在Ruby中有什么区别呢？优先级
或
的优先级非常低，因此
a=b或c
被解释为
（a=b）或c
@Bożena优先级不同，请参见和。非常感谢！但这种优先级是不寻常的，在大多数语言中，赋值的优先级最低。就像Ruby中的许多东西一样，它是从Perl借用的：
puts '>>> assignment = has a higher priority than or <<<'
value = 'y'
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = value or "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

puts '>>> put parenthesis around or expression to have a higher priority than = <<<'
value = 'y'
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = (value or "default_if_value_is_nil")
print 'value=', value.inspect, ', x=', x.inspect, "\n"

puts '>>> || has a higher priority than = <<<'
value = 'y'
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = false
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

value = nil
x = value || "default_if_value_is_nil"
print 'value=', value.inspect, ', x=', x.inspect, "\n"

>>> assignment = has a higher priority than or <<<
value="y", x="y"
value=false, x=false
value=nil, x=nil
>>> put parenthesis around or expression to have a higher priority than = <<<
value="y", x="y"
value=false, x="default_if_value_is_nil"
value=nil, x="default_if_value_is_nil"
>>> || has a higher priority than = <<<
value="y", x="y"
value=false, x="default_if_value_is_nil"
value=nil, x="default_if_value_is_nil"