App Step Modules

appSteps share the properties of all MDI/Shiny modules but have a specific purpose of defining one sequential app step listed on the dashboard sidebar.

See the framework appStep modules for working examples.

appStep UI function

Arguments

In addition to the standard Shiny ‘id’ argument, appStep UI functions must take object ‘options’ as a second argument:

# appStep module ui function, in myAppStep_ui.R
myAppStepUI <- function(id, options)

The options object is a nested R list with the module’s configuration options, as defined by the module’s module.yml and the calling app’s config.yml files.

Element definition

appStep UI functions must create a single UI element as follows:

# appStep module ui function, in myAppStep_ui.R
standardSequentialTabItem(
    title,
    leaderText,
    ... # the UI elements for the appStep's tabbed page
)  

appStep server function

Arguments

In addition to the standard Shiny ‘id’ argument, appStep server functions must take the following additional arguments:

# appStep module server function, in myAppStep_server.R
myAppStepServer <- function(id, options, bookmark, locks)

where:

• options = the same configuration object as passed to the UI function
• bookmark = access to the server bookmark reactive
• locks = access to the server locks reactive

Return value

appStep server functions must return a specifically structured list as a return object to allow proper visibility control for sequential actions and to ensure that proper values are stored in bookmarks.

# appStep module server function, in myAppStep_server.R
# return value
list(
    outcomes = list(   
        myOutcome = reactive()
    ),
    isReady = reactive({ getStepReadiness(...) }),
    ...
)

where:

• outcomes - a list of reactives for use by calling scripts and stored in bookmarks
• isReady - a reactive, or a function that returns a logical, to indicate whether the appStep has been completed; later steps will be masked until isReady() returns TRUE

The list may contain other objects or methods as needed, but they will not be included in bookmarks unless they are a subset of the ‘outcomes’ key and reactive.

Special case: first app steps

Any module used as the first step of an app, i.e., replacing the typical first ‘sourceFileUpload’ module, must also have the following additional members of its returned value list:

# return value
list(
    outcomes = list(
        analysisSetName = reactive(...) # used for default naming of bookmark files
    ),
    loadSourceFile = function(incomingFile, suppressUnlink)  # data passed from the universal launch page
)

Most apps are encouraged to use sourceFileUpload as the first appStep module as it fulfills common requirements in well tested code.