嵌套类实例 (OOP) 上的 R 方法 [英] R methods on nested class instances (OOP)
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问题描述
我有我的学生 S3
班
# a constructor function for the "student" class
student <- function(n,a,g) {
# we can add our own integrity checks
if(g>4 || g<0) stop("GPA must be between 0 and 4")
value <- list(name = n, age = a, GPA = g)
# class can be set using class() or attr() function
attr(value, "class") <- "student"
value
}
我想定义类groupofstudents
:
stud1 <- student("name1", 20, 2.5)
stud2 <- student("name2", 21, 3.5)
groupofstudents <- function(firststud = stud1, secondstud = stud2) {
value <- list(firststud = stud1, secondstud = stud2)
attr(value, "class") <- "groupofstudents"
value
}
gr <- groupofstudents()
但是如果一个类包含来自其他类的数百个其他实例,这似乎不是很有效.
But this doesn't seem to be very efficient in case a class contains hundreds of other instances from other classes.
我所追求的是定义可以修改groupofstudents
中所有学生的字段的方法:
What I am after is to define methods that can modify fields for all students in the groupofstudents
:
getolder <- function(x) UseMethod("getolder")
getolder.groupofstudents <- function(x, years=1) {
x$firststud$age <- x$firststud$age+year
x$secondstud$age <- x$secondstud$age+year
x
}
推荐的方法是什么?
编辑下面对组内所有学生的调用 getolder.student
,但学生没有被修改.
EDIT the below calls getolder.student
on all students of the group, but the students are not modified.
getolder <- function(x) UseMethod("getolder")
getolder.student <- function(x, years=1) {
print("getolder.student called")
x$age <- x$age +1
x
}
getolder.groupofstudents <- function(x, years=1) {
y <- lapply(x$slist, getolder.student)
y
}
getolder(gr) #age increases by 1
stud1 # unchanged, would need to change
stud2 # unchanged, would need to change
EDIT2 这不会改变 gr
和 stud1
、stud2
groupofstudents <- function(slist=NULL) {
value <- list(slist)
attr(value, "class") <- "groupofstudents"
value
}
getolder.groupofstudents <- function(x, years=1) {
#x$slist <- lapply(x$slist, function(y) getolder.student(y, years))
lapply(ls(), function(y) {y1 <- get(y); if(inherits(y1, "student")) assign(y, getolder(y1), envir = .GlobalEnv)})
x
}
gr <- groupofstudents(slist = list("stud1"=stud1, "stud2"=stud2))
gr <- getolder(gr,years=3)
stud1
干杯
推荐答案
R6
是我需要的框架.
# R6 ----------------------------------------------------------------------
student <- R6Class("student", list(
age = 0,
initialize = function(age = 20) {
#stopifnot(is.character(name), length(name) == 1)
stopifnot(is.numeric(age), length(age) == 1)
#self$name <- name
self$age <- age
},
getolder = function(years = 1) {
self$age <- self$age + years
invisible(self)
}
)
)
student$new()
stud1 <- student$new(age = 15)
stud1$getolder(3)
stud1$age #18
stud2 <- student$new(age = 15)
group <- R6Class("group", list(
s1 = NA,
s2 = NA,
initialize = function(s1=NA, s2=NA) {
if(!all(sapply(list(s1, s2), function(x) inherits(x,"student")))) stop("students not students")
self$s1 <- s1
self$s2 <- s2
},
getolder = function(stud, years = 1) {
stud$getolder(years)
invisible(self)
}))
gr1 <- group$new(stud1, stud2)
gr1$s1$age #18
gr1$getolder(gr1$s1, years=10)
gr1$s1$age #28
向 hadley 的 高级 R 书 大喊大叫,它预先指定了 <的可变属性code>R6 对象.
Shout out to hadley's advanced R book which specified upfront the mutable property of R6
objects.
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