Question

这可能看起来像一个奇怪的请求，但我希望暂时附加一个对象，以便可以从所述对象中提取单个元素，但不实际使用attach()或with() 。例如，我很清楚这两种方法可以按名称索引data.frame个元素＆＃34;

obj <- data.frame(N=2, sd=1)

myfun <- function(obj){
    N2 <- obj$N^2
    rnorm(N2, obj$sd)
}
myfun(obj)

myfun2 <- function(obj){
    with(obj, {
        N2 <- N^2
        rnorm(N2, sd)
    })
}
myfun2(obj)

然而，我想要的是更通用的东西，表格可以是

# wanted
myfun3 <- function(){
    N2 <- N^2
    rnorm(N2, sd)
}
with(obj, myfun3()) #this is the idea but clearly doesn't work

因此不需要显式索引obj的元素，并且可以避免将整个语句包装在with()函数中。显然myfun3()找不到obj的内部，但我希望如此。attach(obj) myfun3() detach(obj)以下工作正常，从功能的角度来看正是我想要的，但远非犹太教徒：

attach()

附加通常被认为是错误的，并且为了我的目的，这个代码必须在R包中工作，所以library(parallel) cl <- makeCluster() parfun <- function(index, obj, myfun){ out <- with(obj, myfun()) out } parSapply(cl=cl, 1:100, parfun, obj=obj, myfun=myfun3)甚至不被允许（同样，它嵌套在另一个可以运行的函数中）并行....所以出口到全球环境可能不是一个好的解决方案）。

最终，我希望这一切在安全的并行计算环境中如下工作

import UIKit

class EarthVC: UIViewController {

    @IBOutlet var slideShow1: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.

        slideShow1.animationImages = [

            UIImage(named: "Earth1.jpg")!,
            UIImage(named: "Earth2.jpg")!,
            UIImage(named: "Earth3.jpg")!,
            UIImage(named: "Earth4.jpg")!,
            UIImage(named: "Earth5.jpg")!,
            UIImage(named: "Earth6.jpg")!,
            UIImage(named: "Earth7.jpg")!,
            UIImage(named: "Earth8.jpg")!,
            UIImage(named: "Earth9.jpg")!,
            UIImage(named: "Earth10.jpg")!,
            UIImage(named: "Earth11.jpg")!,
            UIImage(named: "Earth12.jpg")!,
            UIImage(named: "Earth13.jpg")!,
            UIImage(named: "Earth14.jpg")!,
            UIImage(named: "Earth15.jpg")!,
            UIImage(named: "Earth16.jpg")!,
            UIImage(named: "Earth17.jpg")!,
            UIImage(named: "Earth18.jpg")!,
            UIImage(named: "Earth19.jpg")!,
            UIImage(named: "Earth20.jpg")!,
            UIImage(named: "Earth21.jpg")!,
            UIImage(named: "Earth22.jpg")!,
            UIImage(named: "Earth23.jpg")!,
            UIImage(named: "Earth24.jpg")!,
            UIImage(named: "Earth25.jpg")!,
            UIImage(named: "Earth26.jpg")!,
            UIImage(named: "Earth27.jpg")!,
            UIImage(named: "Earth28.jpg")!,
            UIImage(named: "Earth29.jpg")!,
            UIImage(named: "Earth30.jpg")!,
            UIImage(named: "Earth31.jpg")!
        ]

        slideShow1.animationDuration = 93
        slideShow1.startAnimating()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

任何想法都将不胜感激。

Answer 1

怎么样：

do.with  <-  function(context,fun,args=list()){
    env  <-  as.environment(context)
    parent.env(env)  <-  environment(fun)
    environment(fun)  <- env
    do.call(fun,args)
}

context = list(x=1,y=2)
add = function() x + y
do.with(context,add)


context = list(x=2)
parameters = list(y=5)
mult = function(y) x * y
do.with(context,mult,parameters)

不使用attach（）或with（）附加对象

1 个答案: