Turn Features On and Off using Feature Flags.
featureflag
The featureflag
package provides a feature flag (also called as feature toggles, feature switches) implementation for R. Feature flags allow developers to turn functionalities on and off based on configuration.
If you are interested in learning more about feature flags, check out those great resources:
- https://martinfowler.com/articles/feature-toggles.html
- https://featureflags.io/
- https://en.wikipedia.org/wiki/Feature_toggle
Installation
Install the development version from GitHub with:
# install.packages("devtools")
devtools::install_github("szymanskir/featureflag")
Examples
Simple example
The featureflag
package currently supports one type of feature flags: bool feature flags (simple on and off flags):
library(featureflag)
my_feature_flag <- create_bool_feature_flag(TRUE)
if (is_enabled(my_feature_flag)) {
print("My feature is enabled!")
} else {
print("My feature is not enabled!")
}
if and if/else helpers
featureflag
provides helpers that allow you to omit boilerplate code such as if
or if/else
. They can be replace by the usage of feature_if
or feature_ifelse
accordingly:
feature_ifelse(
my_feature_flag,
print("My feature is enabled!"),
print("My feature is not enabled!")
)
Shiny example
The source code of all examples is available in the examples folder of the repository.
Feature flags can be especially useful when developing shiny applications. The example below shows how feature flags can be used to turn parts application on and off – in this case an extra instance of the counter module.
FLAGS <- list(
extra_counter_flag = create_bool_feature_flag(value = FALSE)
)
ui <- fluidPage(
counterButton("counter1", "Always Visible Counter"),
feature_if(FLAGS$extra_counter_flag, {
counterButton("flagged_counter", "Flagged Counter")
})
)
server <- function(input, output, session) {
counterServer("counter1")
feature_if(FLAGS$extra_counter_flag, {
counterServer("flagged_counter")
})
}
Defining feature flags in configuration files
The featureflag
package can also be used in combination with the config package by using the R code execution feature:
default:
extra_counter_flag: !expr featureflag::create_bool_feature_flag(value = TRUE)
test:
extra_counter_flag: !expr featureflag::create_bool_feature_flag(value = TRUE)
production:
extra_counter_flag: !expr featureflag::create_bool_feature_flag(value = FALSE)
Create your own feature flag
You can create feature flags that are turned on based on your own custom criteria. The procedure on how to define your own feature flag is presented in this tutorial.