R: Custom output handlers.

new_output_handler {evaluate} | R Documentation

## Custom output handlers.

### Description

An `output_handler` handles the results of `evaluate`, including the values, graphics, conditions. Each type of output is handled by a particular function in the handler object.

### Usage

    new_output_handler(source = identity, text = identity, graphics = identity,
        message = identity, warning = identity, error = identity, value = render)

### Arguments

`source` | Function to handle the echoed source code under evaluation.
`text` | Function to handle any textual console output.
`graphics` | Function to handle graphics, as returned by `recordPlot`.
`message` | Function to handle `message` output.
`warning` | Function to handle `warning` output.
`error` | Function to handle `stop` output.
`value` | Function to handle the values returned from evaluation. If it only has one argument, only visible values are handled; if it has more arguments, the second argument indicates whether the value is visible.

### Details

The handler functions should accept an output object as their first argument. The return value of the handlers is ignored, except in the case of the `value` handler, where a visible return value is saved in the output list.

Calling the constructor with no arguments results in the default handler, which mimics the behavior of the console by printing visible values.

Note that recursion is common: for example, if `value` does any printing, then the `text` or `graphics` handlers may be called.

### Value

A new `output_handler` object

[Package evaluate version 0.11 Index]