Question

我有一个函数open.account，它接受一个参数'total'并创建一个包含三个函数的列表（存款，取款，余额）。如果我运行test <- open.account(100)，如何在不调用其中一个列表函数的情况下直接访问测试总值？

    open.account <- function(total) {
  list(
    deposit = function(amount) {
      if(amount <= 0)
        stop("Deposits must be positive!\n")
      total <<- total + amountw
      cat(amount, "deposited.  Your balance is", total, "\n\n")
    },
    withdraw = function(amount) {
      if(amount > total)
        stop("You don't have that much money!\n")
      total <<- total - amount
      cat(amount, "withdrawn.  Your balance is", total, "\n\n")
    },
    balance = function() {
      cat("Your balance is", total, "\n\n")
    }
  )
}

Answer 1

每个返回的函数都有自己的环境，其中存储了total。

g <- open.account(total = 100)

environment(g$deposit)
# <environment: 0x279d0b0>
ls(environment(g$deposit))
# [1] "total"
environment(g$deposit)$total
# [1] 100

如何显示函数创建的列表对象的参数值

1 个答案: