kitems

The goal of kitems is to provide a framework to manage data frame items and a set of tools to implement it within Shiny web applications.

It is delivered as a Shiny module.

Installation

The development (beta) version of kitems can be installed from GitHub with:

# install.packages("devtools")
devtools::install_github("thekangaroofactory/kitems")

Note that the package is under development convergence.
Features may still be modified at this stage, and there is no guaranty that exported functions signature will not change before it is converged.

Demo

Demo apps are delivered together with the package and can be accessed with:

library(kitems)

# -- get example demo name
runExample()

Framework Specifications

The kitems framework is based on two main notions - data model and items.

Data Model

The data model contains the specifications of the items to manage.

For each attribute, the data model carries information like its name and type, but also a method to determine its default value and logical values to indicate if it should be skipped in forms, filtered from the table view or used to sort the data.

Supported types are numeric, integer, logical, character, factor, Date and POSIXct.

Note: class POSIXlt is not supported as it stores datetime values into a list
POSIXct should be used to store datetime attributes.

Items

Items are stored in a data frame that fits with the data model rules.
That means the data model is implemented in all functions related to item management.

Path

Both data model & item files are stored in a specific folder dedicated to that instance of the module.
The folder is named after the id of the module.

For this reason, unless there is a single instance of the module, it is not recommended to name any of the id with same name as the last folder of the provided path.

Example:

• path = "./path/to/data" & id = "data" will store files in “./path/to/data”
• path = "./path/to/data" & id = "data_1" will store files in “./path/to/data/data_1”

It may result in files being stored at different levels.

Reactive Values

kitems strongly relies on Shiny (both shiny and shinydashboard packages are set as ‘depends’ dependencies).

It delivers reactive values that are accessible from the module server return value.

The return value has the following structure:

list(id,
     url,
     items,
     data_model,
     filtered_items,
     selected_items,
     clicked_column,
     filter_date)

Data model and items reactive values should be handled with caution as updating there values will trigger auto save (if autosave = TRUE).

Data Model

The data model can be accessed in a reactive context from the return value list, as data_model()

library(kitems)

# -- call module
mydata <- kitems_server(id = "my_data_id", path = "path/to/my/data")

# -- get data model
data_model <- mydata$data_model()

Items

The items for this id can be accessed in a reactive context from the return value list, as items()

# -- call module
mydata <- kitems_server(id = "my_data_id", path = "path/to/my/data")

# -- get items
items <- mydata$items()

Observe reactive values

The module server return value holds references to the reactives values.
Here is an example how to observe the items:

# -- Call module server
mydata <- kitems(id = "mydata", path = "./data")

# -- Observe items
observeEvent(mydata$items(), {
  cat("Main application server: items object has just been updated. \n")
  # -- do something cool here
  })

Note: when observing the filtered_items from the main application, it’s recommended to add the ignoreInit = TRUE parameter (or use bindEvent for render* functions) in order to avoid multiple computations at start-up.

Data model

Initialization

When starting the module with id and path arguments, it will check if the corresponding data model is available in the destination path.

If no data model is found, the admin UI will display a button to create a new data model, as well as a button to import data (it creates the data model from the data).

Checking integrity

When the module server is launched, it will perform an integrity check to ensure that the items and data model are synchronized.

If not, the data model will be updated to match with any missing attribute for example.
Items will be checked as well to make sure attribute types fit with the data model.

Item management

The create and update buttons triggers a dynamic form that is built based on the data model.
Attributes defined as skipped won’t get an input in the form.
The inputs are initialized with the default values or output of the default functions when defined.
After the form is completed, a check is performed to make sure values match the attribute types.
If no value is provided for an attribute, the default is applied.

Views

Filtered view

A filtered view, based on the filtered_items content is delivered with data model masks applied.
Filtered attributes will be hidden, and items will be ordered as defined in the data model.

Selected Item(s)

The filtered view have row selection enabled.
Selecting row(s) in the table will trigger the update of selected_items reactive value.
Selected item(s) will also trigger which buttons are available (delete is not visible if no item is selected).

Inputs

Date sliderInput

If the data model has an attribute named ‘date’, a date sliderInput will be created automatically to enable date filtering. If not implemented in the main application UI, it will have no impact on the filtered items.

Buttons

Standard buttons are delivered to trigger the module server actions.
They are implemented as separate UI functions so that it’s possible to wrap them into a more complex UI function.

• create
• update (single item selection)
• delete (supports multi-selection)

Administration

Admin console

An admin console is delivered as a standalone Shiny app.
The reason is that in most cases, it’s not recommended to have the data model(s) management accessible from within the application.

The admin console gives access to all the data models belonging to the path argument in one place.

Nested module considerations

In case the kitems module server function is called from inside a module (i.e. as a nested module), then it is not possible to call the UI functions from the main app with the nested module id.

From there, two options are available:

• wrap the package UI functions into functions from the calling module (encapsulation)
  For example, create a UI function that implements the different buttons into a single UI delivered by the calling module.

• call the package UI functions directly from the main app using multiple namespaces:
  (as specified in the shiny::NS function)

 kitems::admin_ui(c("module_id", "nested_module_id"))