ruby 中“&:”运算符的功能是什么？
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what is the functionality of "&: " operator in ruby?
提问by Rahul
Possible Duplicate:
What does map(&:name) mean in Ruby?
I came across a code snippet which had the following
我遇到了一个代码片段，其中包含以下内容
a.each_slice(2).map(&:reverse)
I do not know the functionality of &:operator. How does that work?
我不知道&:运算符的功能。这是如何运作的？
回答by Gareth
There isn't a &:operator in Ruby. What you are seeing is the &operator applied to a :symbol.
&:Ruby 中没有运算符。您看到的是&应用于 a的运算符:symbol。
In a method argument list, the &operator takes its operand, converts it to a Procobject if it isn't already (by calling to_procon it) and passes it to the method as if a block had been used.
在方法参数列表中，&操作符获取它的操作数，Proc如果它还没有（通过调用to_proc它）将其转换为对象，并将其传递给方法，就像使用了块一样。
my_proc = Proc.new { puts "foo" }
my_method_call(&my_proc) # is identical to:
my_method_call { puts "foo" }
So the question now becomes "What does Symbol#to_procdo?", and that's easy to see in the Rails documentation:
所以问题现在变成了“做Symbol#to_proc什么？”，这在Rails 文档中很容易看到：
Turns the symbol into a simple proc, which is especially useful for enumerations. Examples:
将符号变成一个简单的过程，这对枚举特别有用。例子：
# The same as people.collect { |p| p.name }
people.collect(&:name)
# The same as people.select { |p| p.manager? }.collect { |p| p.salary }
people.select(&:manager?).collect(&:salary)
回答by KL-7
By prepending &to a symbol you are creating a lambda function that will call method with a name of that symbol on the object you pass into this function. Taking that into account:
通过添加&一个符号，您将创建一个 lambda 函数，该函数将在传递给此函数的对象上调用具有该符号名称的方法。考虑到这一点：
ar.map(&:reverse)
is roughly equivalent to:
大致相当于：
ar.map { |element| element.reverse }
