R/varbundle-utils.R

In loudermilk/VarBundle: Read-Only Variable Bundles

# Convert value to type
# Casts character val to type
# @param val (character)
# @param type (character)
# @return object
convert <- function(val, type) {
  conv_val <- switch(type,
                      "character" = as.character(val),
                      "numeric" = as.numeric(val),
                      "integer" = as.integer(val),
                      "logical" = as.logical(val),
                      "complex" = as.complex(val)
  )
  conv_val
}

# @title Data.frame to List
#
# @description Helper function to create a list from a data.frame so that a
# VarBundles can be created. Currently only "simple" lists can be created by
# this method (i.e. all elements of the list are atomic scalars - no vectors,
# lists, data.frames, etc).
#
# Designed to work with a persistence mechanism that allows users to easily mod
# an external file (e.g., configuration values) to be used to instantiate
# a VarBundle object.
#
# var   val   type
# <chr> <chr> <chr>
# 1 a   1     numeric
# 2 b   foo   character
# 3 c   TRUE  logical
# 4 d   3.14  numeric
#
# The df must be nx3, with column headers "var", "val", "type" and all cols of type
# character. The type col can only contain values of "character", "numeric",
# "integer", "logical", or "complex" - this information is used to convert
# the character values in the "val" column to the appropriate type.
df_to_list <- function(df) {
  vals <- lapply(1:nrow(df), function(i) {
    var <- df$var[i]
    val <- df$val[i]
    type <- df$type[i]

    convert(val, type)
  })
  ll <- stats::setNames(vals, df$var)
  return(ll)
}