Extend blockr

blockr's plugin system lets you customize how the application behaves: add new UI panels, modify block interactions, or change how the board works.

Plugin architecture

A plugin is an R object with hooks that fire at specific points in the blockr lifecycle. Plugins can:

• Add custom UI to the board (sidebars, toolbars, modals)
• Intercept block creation and deletion
• Modify how blocks connect
• Add new controls to individual blocks

new_my_plugin <- function() {
  new_plugin(
    # UI added to the board
    ui = function(id) {
      ns <- shiny::NS(id)
      shiny::actionButton(ns("my_btn"), "Custom action")
    },
    # Server logic
    server = function(id, board) {
      shiny::moduleServer(id, function(input, output, session) {
        shiny::observeEvent(input$my_btn, {
          # React to custom UI
        })
      })
    },
    class = "my_plugin"
  )
}

Custom block UI

Override how any block renders its UI using S3 methods. This lets package authors customize the appearance of their blocks without modifying blockr.core:

# Custom UI for your block class
block_ui.my_block <- function(block, id) {
  ns <- shiny::NS(id)
  bslib::card(
    bslib::card_header("My Custom Block"),
    bslib::card_body(
      shiny::selectInput(ns("column"), "Column", choices = NULL)
    )
  )
}

Block registry

The registry is the "supermarket" for blocks. It tracks all available blocks with metadata (name, description, category, package). When you load a blockr extension package, its blocks are automatically registered via .onLoad() and appear in the block menu.

# Query available blocks
available_blocks()

# Register a new block
register_block(
  constructor = new_my_block,
  name = "My block",
  description = "Does something useful",
  category = "transform"
)

# Unregister a block
unregister_block("my_block")

This makes collaboration easy: one team builds a package of domain-specific blocks, registers them, and they appear in every user's block menu.

Further reading

• Full extend-blockr vignette: complete plugin examples
• Block registry vignette: registry internals
• blockr.core API reference: full function documentation