Dynamic multi-row input for repeating groups of inputs

A custom Shiny input that lets users dynamically add and remove rows, where each row is a group of heterogeneous inputs (e.g. a select, a text box, a colour picker, and a numeric input on one line). A + Add button appends a row; an X button on each row deletes it. Rows are added and removed entirely on the client by cloning a hidden template and letting Shiny bind the new inputs, mirroring the architecture of multiColorPicker().

Usage

multiDynamicInput(
  inputId,
  label = NULL,
  row_spec,
  elements = NULL,
  max_per_row = 4,
  add_label = "+ Add",
  width = NULL,
  panel = TRUE
)

Arguments

inputId

Character. Shiny input id.

label

Optional label displayed next to the add button.

row_spec

A named list describing one row. Each element is itself a list specifying a single field, with either:

• type — a string alias: one of "select", "text", "numeric", "slider", "checkbox", "colour"/"color"; or

• fn — an input constructor function (e.g. shiny::dateInput).

plus an optional args list of arguments passed to the constructor (everything except inputId, which is generated per row). The element name becomes the key under which that field's value is returned.

elements

Optional initial rows to display on startup. A named list of rows (each a named list keyed by the row_spec names) in the same shape as the return value. For example: list(models1 = list(model_type = "lm", formula = "y ~ x", line_colour = "#FF0000", line_width = 2)).

max_per_row

Integer. Maximum number of fields on one visual line before wrapping. Default 4.

add_label

Character. Label for the add button. Default "+ Add".

width

Optional CSS width for the container.

panel

Logical. If FALSE, removes the surrounding panel/well styling.

Value

A UI element that produces a named list of rows.

Details

The value reported to input[[inputId]] is a named list of rows (model1, model2, ...), each a named list keyed by the row_spec names.

The component is generic over input type. Each field in row_spec is described by an input constructor and its arguments, so any Shiny input that takes inputId as its first argument can be used. Common types have a short type = "..." alias.

Author

Jacob Martin

Examples

if (interactive()) {
    library(shiny)

    ui <- fluidPage(
        multiDynamicInput(
            "models",
            label = "Models",
            row_spec = list(
                model_type  = list(type = "select",
                    args = list(choices = c("lm", "glm", "loess", "nls"))),
                formula     = list(type = "text",
                    args = list(placeholder = "y ~ poly(x, 2)")),
                line_colour = list(type = "colour", args = list(value = "#000000"))
            )
        ),
        verbatimTextOutput("chosen")
    )

    server <- function(input, output, session) {
        output$chosen <- renderPrint(input$models)
    }

    shinyApp(ui, server)
}