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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/print.R
\name{cli_format_method}
\alias{cli_format_method}
\title{Create a format method for an object using cli tools}
\usage{
cli_format_method(expr, theme = getOption("cli.theme"))
}
\arguments{
\item{expr}{Expression that calls \verb{cli_*} methods, \code{\link[base:cat]{base::cat()}} or
\code{\link[base:print]{base::print()}} to format an object's printout.}
\item{theme}{Theme to use for the formatting.}
}
\value{
Character vector, one element for each line of the printout.
}
\description{
This method can be typically used in \code{format()} S3 methods. Then the
\code{print()} method of the class can be easily defined in terms of such a
\code{format()} method. See examples below.
}
\examples{
# 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 <- function(pkg) {
tryCatch(
desc <- packageDescription(pkg),
warning = function(e) stop("Cannot find R package `", pkg, "`")
)
file <- dirname(attr(desc, "file"))
if (basename(file) != pkg) file <- dirname(file)
structure(
list(desc = unclass(desc), lib = dirname(file)),
class = "r_package"
)
}
format.r_package <- 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 <- 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 <- options(cli.theme = simple_theme())
print(new_r_package("cli"))
options(opt) # <- restore theme
}
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