您可以在R中通过引用吗? [英] Can you pass-by-reference in R?

问题描述

可以通过引用传递"R"吗? 例如，在以下代码中:

Can you pass by reference with "R" ? for example, in the following code:

setClass("MyClass",
    representation(
    name="character"
    ))


instance1 <-new("MyClass",name="Hello1")
instance2 <-new("MyClass",name="Hello2")

array = c(instance1,instance2)

instance1
array

instance1@name="World!"

instance1
array

输出为

> instance1
An object of class "MyClass"
Slot "name":
[1] "World!"

> array
[[1]]
An object of class "MyClass"
Slot "name":
[1] "Hello1"


[[2]]
An object of class "MyClass"
Slot "name":
[1] "Hello2"

但我希望是

> instance1
An object of class "MyClass"
Slot "name":
[1] "World!"

> array
[[1]]
An object of class "MyClass"
Slot "name":
[1] "World!"


[[2]]
An object of class "MyClass"
Slot "name":
[1] "Hello2"

有可能吗?

推荐答案

否.

赋值语句中的对象是不可变的. R将复制对象而不是只是引用.

Objects in assignment statements are immutable. R will copy the object not just the reference.

> v = matrix(1:12, nrow=4)
> v
           [,1] [,2] [,3]
     [1,]    1    5    9
     [2,]    2    6   10
     [3,]    3    7   11
     [4,]    4    8   12
> v1 = v
> v1[,1]     # fetch the first column 
     [1] 1 2 3 4

( proviso :以上陈述适用于R 基元，例如向量，矩阵)，也适用于函数；我不能肯定地说 all R个对象是否正确-只是大多数对象，以及绝大多数最常用的对象.)

(proviso: the statement above is true for R primitives, e.g., vectors, matrices), and also for functions; I cannot say for certain whether it's true for all R objects--just most of them, as well as the vast majority of the ones most often used.)

如果您不喜欢这种行为，则可以在R软件包的帮助下选择退出.例如，有一个名为 R.oo 的R包，它可以让您模仿按引用传递行为； R.oo在 CRAN 中可用.

If you don't like this behavior you can opt out of it with the help from an R Package. E.g., there is an R Package called R.oo that allows you to mimic pass-by-reference behavior; R.oo is available on CRAN.

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