在Ruby中通过引用传递参数?

In Ruby, is it possible to pass by reference a parameter with value-type semantics (e.g. a Fixnum)? I'm looking for something similar to C#'s 'ref' keyword.

在Ruby中，是否可能通过引用传递具有值类型语义的参数(例如一个Fixnum)?我在找一些类似c# 's 'ref'关键字的东西。

Example:

例子:

def func(x) 
    x += 1
end

a = 5
func(a)  #this should be something like func(ref a)
puts a   #should read '6'

Btw. I know I could just use:

顺便说一句。我知道我可以用:

a = func(a)

5 个解决方案

#1

You can accomplish this by explicitly passing in the current binding:

您可以通过显式地传入当前绑定来实现这一点:

def func(x, bdg)
  eval "#{x} += 1", bdg
end

a = 5
func(:a, binding)
puts a # => 6

#2

Ruby doesn't support "pass by reference" at all. Everything is an object and the references to those objects are always passed by value. Actually, in your example you are passing a copy of the reference to the Fixnum Object by value.

Ruby根本不支持“引用传递”。一切都是一个对象，对这些对象的引用总是通过值传递。实际上，在您的示例中，您正在按值将引用的副本传递给Fixnum对象。

The problem with the your code is, that x += 1 doesn't modify the passed Fixnum Object but instead creates a completely new and independent object.

您的代码的问题是，x += 1不修改传递的Fixnum对象，而是创建一个全新的、独立的对象。

I think, Java programmers would call Fixnum objects immutable.

我认为，Java程序员会把Fixnum对象称为不可变的。

#3

In Ruby you can't pass parameters by reference. For your example, you would have to return the new value and assign it to the variable a or create a new class that contains the value and pass an instance of this class around. Example:

在Ruby中，不能通过引用传递参数。对于您的示例，您必须返回新的值并将其分配给变量a，或者创建一个包含该值的新类，并传递该类的实例。例子:

class Container
attr_accessor :value
 def initialize value
   @value = value
 end
end

def func(x)
  x.value += 1
end

a = Container.new(5)
func(a)
puts a.value

#4

You can try following trick:

你可以试试下面的技巧:

def func(x) 
    x[0] += 1
end

a = [5]
func(a)  #this should be something like func(ref a)
puts a[0]   #should read '6'

#5

http://ruby-doc.org/core-2.1.5/Fixnum.html

Fixnum objects have immediate value. This means that when they are assigned or passed as parameters, the actual object is passed, rather than a reference to that object.

Fixnum对象具有立即的值。这意味着当它们作为参数分配或传递时，实际的对象被传递，而不是对该对象的引用。

Also Ruby is pass by value.

Ruby也是通过值传递的。

#1