Generate function to get or set global options
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README.md

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GlobalOptions

This package aims to provide a simple way to handle global configurations. It can:

  1. validate the values (e.g. class, length and self-defined validations);
  2. set read-only options;
  3. set invisible options;
  4. set private options which are only accessable in a certain namespace.
  5. support local options and global options

There is a vignette in the package which explains with more detail.

Usage

The most simple way is to construct an option function (e.g. opt()) as:

library(GlobalOptions)
opt = set_opt(
    "a" = 1,
    "b" = "text"
)

Then users can get or set the options by:

opt()
opt("a")
opt$a
opt[["a"]]
opt(c("a", "b"))
opt("a", "b")
opt("a" = 2)
opt$a = 2
opt("a" = 2, "b" = "new_text")

Users can reset their default values by:

opt(RESET = TRUE)

Advanced control on options

The value for each option can be set as a list which may contain more configurations on the option:

opt = set_opt(
    "a" = list(.value = 1,
               .length = 1,
               .class = "numeric",
               .validate = function(x) x > 0,
               .failed_msg = "'a' should be a positive number.",
               .filter = function(x) ifelse(x > 10, 10, x),
               .read.only = FALSE,
               .visible = TRUE,
               .private = FALSE),
    "b" = "text"
)

In above example, option value for a should pass following conditions:

  1. length should be 1;
  2. should have numeric class;
  3. should be positive;
  4. if the value is larger than 10, it will be enforced to 10.

Other fields mean:

  1. default value of a is 1;
  2. it is not read-only;
  3. it is visible;
  4. it is public.

Dynamic option values

If the value of the option is set as a function and the class of the option is non-function. The function will be executed everytime when querying the option. In following example, the prefix option controls the prefix of the log message.

opt = set_opt(
    prefix = list(.value = function() paste("[", Sys.time(), "] ", sep = " "),
                  .class = "character")
)

Then opt("prefix") will return the current time:

opt("prefix")

## [1] "[ 2015-08-18 17:49:06 ] "

Sys.sleep(2)
opt("prefix")

## [1] "[ 2015-08-18 17:49:08 ] "

Interact between options

One option value can depend on other option values and the value of the option changes when the value of the dependent option changes.

opt = set_opt(
    a = 1,
    b = function() .v$a * 2
)
opt()

## $a
## [1] 1
## 
## $b
## [1] 2

opt(a = 2); opt()

## $a
## [1] 2
## 
## $b
## [1] 4

Local options

Local options can be created by specifying LOCAL to TRUE. The local mode will end when LOCAL is set to FALSE explicitely or the environment changes.

opt = set_opt(
    a = 1
)

f1 = function() {
    opt(LOCAL = TRUE)
    opt(a = 2)
    return(f2())
}
f1()

## [1] 2

opt("a")

## [1] 1

License

MIT