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Filtering Items

Introduction

Kitems provides standard features to enable automatic data filtering.

Reminder

The module server returns a composite value that includes references to reactive values:

  • items

  • filtered_items

  • filter_date

# -- call module server
mydata <- kitems(id = "myid")

# -- access the data
mydata$items()
mydata$filtered_items()
mydata$filter_date()

Widgets

Item table

The item table widget is by default a filtered view of the items.
It displays the content of filtered_items() .

It is delivered through the filtered_view_ui function.

The reason for not having a non filtered item table is that if the goal is to display the whole list of items without any filtering, then there would be no added value compared to using the renderDT / DTOutput functions directly in the main Shiny application.

As of now, only date filtering support has been implemented.

Date slider

The date slider widget is automatically enabled when the data model contains an attribute that is named ‘date’ (strictly) and accessible through the date_slider_INPUT function.

Screenshot of the widget

Its behavior is driven by two strategies:

  • ‘this-year’ – automatically selects and extends the range of date belonging to current year upon item operations (this is the default).

  • ‘keep-range’ – keeps the selected range no matter if items are added or removed 1

When the server is initialized, it will scan the items to setup the dateSliderInput range to the minimum and maximum of the date column, and the selected range to the values fitting with current year. 2

Reactive lifecycle

Whenever the date range value is modified in the widget, it will trigger two actions in the reactive lifecycle of the module server:

  • filter_date will be updated with the value of the slider input 3

  • filtered_items will be updated with the items fitting with the selected date range 4

Considerations

Initialization

The most important notion to understand when it comes to the initialization of the filtered_items (and its view) is that when the module server is launched, there is no way to determine if the main application will implement the date slider widget.

The module server checks the data model for a ‘date’ attribute and creates an output that will be accessible through the date_slider_INPUT function. But it can’t guess if it’s actually going to be implemented of not.

For this reason, the filtered_items reactive value is initialized with the same value as items.

This means, if the content of filtered_items is reused within the main application - for example to build a plot - it is strongly advised to check if filter_date is NULL or not to avoid computing the plot twice.

It can be done by implementing one of the following options in the renderPlot expression:

  • check if the filter input is “truthy” with req(mydata$filter_date())

  • use bindEvent function on the filtered_items with ignoreInit = FALSE