问题
一般问题
您将如何开始在 R 中实现PicoContainer-Framework？
具体问题
“微微注册表（机制）”实际上会是什么样子？我想出了一个“穷人的版本”，它只适用于单个注册过程（参见DefaultPicoContainer下面示例中的类；此时方法getComponentInstance()实际上并没有利用信息getRefClass("MovieLister")来查找注册的组件）
例子
AFAIU，R 中还没有任何PicoContainer-Framework的实现，所以我考虑了它的外观。
到目前为止，这是我能想到的。它的灵感来自Martin Fowler关于依赖注入的文章。
1.业务逻辑层示例
接口（类）MovieFinder
setRefClass(
Class="MovieFinder",
contains=c("VIRTUAL"),
methods=list(
findAll=function() {}
)
)
班级MovieLister
setRefClass(
Class="MovieLister",
fields=list(
finder="MovieFinder"
),
methods=list(
initialize=function(finder=NULL) {
callSuper(finder=finder)
},
moviesDirectedBy=function(arg) {
allMovies <- finder$findAll()
out <- lapply(seq(along=nrow(allMovies)), function(ii) {
movie <- allMovies[ii,]
out <- movie
if (movie$director != arg) {
out <- NULL
}
return(out)
})
out
}
)
)
班级ColonMovieFinder
setRefClass(
Class="ColonMovieFinder",
contains=c("MovieFinder"), ## Implements the 'MovieFinder' interface
fields=list(
filename="character"
),
methods=list(
initialize=function(filename) {
callSuper(filename=filename)
},
findAll=function() {
read.table(.self$filename)
}
)
)
2. R中Pico容器框架的适配
班级ConstantParameter
setRefClass(
Class="ConstantParameter",
fields=list(
para="ANY"
),
methods=list(
initialize=function(para) {
callSuper(para=para)
}
)
)
班级DefaultPicoContainer
setRefClass(
Class="DefaultPicoContainer",
fields=list(
.class="refObjectGenerator",
.dependency="list"
),
methods=list(
registerComponentImplementation=function(...) {
x <- list(...)
if (length(x) == 1) {
.self$.class <- x[[1]]
} else {
.self$.dependency <- x
}
TRUE
},
getComponentInstance=function(classobj) {
deps <- rev(.self$.dependency)
inst <- NULL
for (ii in 1:length(deps)) {
inst.args <- NULL
if (ii == 1) {
inst.args <- lapply(deps[[ii]], "[[", "para")
inst.gen <- deps[[ii + 1]]
inst <- do.call(inst.gen$new, args=inst.args)
} else if (ii < length(deps)){
inst.gen <- deps[[ii + 1]]
if (!isVirtualClass(Class=inst.gen$className)) {
inst <- do.call(inst.gen$new, args=list(inst))
}
}
}
inst
}
)
)
功能configurecontainer
configureContainer <- function() {
pico <- new("DefaultPicoContainer")
finderParams <- list(
new("ConstantParameter", "movies1.txt")
)
pico$registerComponentImplementation(
getRefClass("MovieFinder"),
getRefClass("ColonMovieFinder"),
finderParams
)
pico$registerComponentImplementation(
getRefClass("MovieLister")
)
return(pico)
}
3. 测试
尽管我知道这个测试实际上超出了纯单元测试的范围，但我还是使用了单元测试。
require("testthat")
test_that(desc="test_testWithPico",
code={
## Example 'movies1.txt' file //
movies <- data.frame(
movie=c("A", "B", "C"),
director=c("Director 1", "Director 2", "Director 3")
)
write.table(x=movies, file="movies1.txt", sep="")
## Create new pre-configured pico container //
pico <- configureContainer()
## Use pico container in Business Logic Layer //
lister <- new("MovieLister",
finder=pico$getComponentInstance(getRefClass("MovieLister"))
)
movies <- lister$moviesDirectedBy("Director 1")
## Assert //
target <- list(data.frame(movie="A", director="Director 1"))
expect_that(
movies,
is_equivalent_to(target)
)
}
)
背景
我开始着迷于面向对象设计的SOLID原则，尤其是依赖倒置和依赖注入的概念/原则，并希望开始在我的 R 程序中遵循它们。
非常感谢任何有关如何在 R 中最好地遵循这些原则的指针