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<table width="100%" summary="page for cli_format_method {cli}"><tr><td>cli_format_method {cli}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Create a format method for an object using cli tools</h2>

<h3>Description</h3>

<p>This method can be typically used in <code>format()</code> S3 methods. Then the
<code>print()</code> method of the class can be easily defined in terms of such a
<code>format()</code> method. See examples below.
</p>

<h3>Usage</h3>

<pre>
cli_format_method(expr, theme = getOption("cli.theme"))
</pre>

<h3>Arguments</h3>

<table summary="R argblock">
<tr valign="top"><td><code>expr</code></td>
<td>
<p>Expression that calls <code style="white-space: pre;">cli_*</code> methods, <code><a href="../../base/html/cat.html">base::cat()</a></code> or
<code><a href="../../base/html/print.html">base::print()</a></code> to format an object's printout.</p>
</td></tr>
<tr valign="top"><td><code>theme</code></td>
<td>
<p>Theme to use for the formatting.</p>
</td></tr>
</table>

<h3>Value</h3>

<p>Character vector, one element for each line of the printout.
</p>

<h3>Examples</h3>

<pre>

# Let's create format and print methods for a new S3 class that
# represents the an installed R package: `r_package`

# An `r_package` will contain the DESCRIPTION metadata of the package
# and also its installation path.
new_r_package &lt;- function(pkg) {
  tryCatch(
    desc &lt;- packageDescription(pkg),
    warning = function(e) stop("Cannot find R package `", pkg, "`")
  )
  file &lt;- dirname(attr(desc, "file"))
  if (basename(file) != pkg) file &lt;- dirname(file)
  structure(
    list(desc = unclass(desc), lib = dirname(file)),
    class = "r_package"
  )
}

format.r_package &lt;- function(x, ...) {
  cli_format_method({
    cli_h1("{.pkg {x$desc$Package}} {cli::symbol$line} {x$desc$Title}")
    cli_text("{x$desc$Description}")
    cli_ul(c(
      "Version: {x$desc$Version}",
      if (!is.null(x$desc$Maintainer)) "Maintainer: {x$desc$Maintainer}",
      "License: {x$desc$License}"
    ))
    if (!is.na(x$desc$URL)) cli_text("See more at {.url {x$desc$URL}}")
  })
}

# Now the print method is easy:
print.r_package &lt;- function(x, ...) {
  cat(format(x, ...), sep = "\n")
}

# Try it out
new_r_package("cli")

# The formatting of the output depends on the current theme:
opt &lt;- options(cli.theme = simple_theme())
print(new_r_package("cli"))
options(opt)  # &lt;- restore theme
</pre>

<hr /><div style="text-align: center;">[Package <em>cli</em> version 3.4.1 <a href="00Index.html">Index</a>]</div>
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