Reactive object bindings in a non-shiny context

Question

Actual question

How could you either approximate the reactive environment/behavior established by shiny functions or possibly even use these very functions in a

Answer 1

There is a collection of test_that unit tests in location /usr/local/lib/R/site-library/shiny/tests/. They give you a good idea of how the functions/wrappers:

• reactiveValues
• reactive
• observe
• isolate

can be used outside of a shinyServer call.

The key is to use flushReact to make the reactivity fire off. Here, for example, is one of the tests in file test-reactivity.r, and I think it already gives you a good sense of what you need to do:

test_that("overreactivity2", {
  # ----------------------------------------------
  # Test 1
  # B depends on A, and observer depends on A and B. The observer uses A and
  # B, in that order.

  # This is to store the value from observe()
  observed_value1 <- NA
  observed_value2 <- NA

  values <- reactiveValues(A=1)
  funcB  <- reactive({
    values$A + 5 
  })  
  obsC <- observe({
    observed_value1 <<-  funcB() * values$A
  })  
  obsD <- observe({
    observed_value2 <<-  funcB() * values$A
  })  

  flushReact()
  expect_equal(observed_value1, 6)   # Should be 1 * (1 + 5) = 6
  expect_equal(observed_value2, 6)   # Should be 1 * (1 + 5) = 6
  expect_equal(execCount(funcB), 1)
  expect_equal(execCount(obsC), 1)
  expect_equal(execCount(obsD), 1)

  values$A <- 2
  flushReact()
  expect_equal(observed_value1, 14)  # Should be 2 * (2 + 5) = 14
  expect_equal(observed_value2, 14)  # Should be 2 * (2 + 5) = 14
  expect_equal(execCount(funcB), 2)
  expect_equal(execCount(obsC), 2)
  expect_equal(execCount(obsD), 2)
})