在rmarkdown和knitr中打印自定义对象（PDF和HTML）

假设我有一个包，其中包含一个返回S3对象的函数：

---

使用knitr 1.18的new_myclass更简单：

guess_output_format <- function() {
  if (knitr::is_html_output()) {
    return("html")
  } else if (knitr::is_latex_output()) {
    return("latex")
  } else {
    return("unsupported")
 }
}

guess\u输出\u格式
#'---
#' title: My document
#' output: pdf_output
#'---

knit_print.myclass <- function(x, ...) {
  rmarkdown_fmt <- rmarkdown::metadata$output
  knitr_fmt <- knitr::opts_knit$get("out.format")
  # should I use these heuristics with both variables?
  if (rmarkdownfmt == "pdf_document") {
    return(knitr::asis_output(myclass2latex(x)))
  }
  if (knitr_fmt %in% c("html", "markdown")) {
    return(knitr::asis_output(myclass2html(x)))
  } else {
    stop("Format not supported!")
  }
}

#' @importFrom rmarkdown metadata
#' @importFrom knitr opts_knit
guess_output_format <- function() {
  rmd_output <- tryCatch({rmarkdown::metadata$output},
                         error = function(e) {NULL})
  if (is.null(rmd_output)) {
    rmd_output = ""
  }
  if (is.list(rmd_output)) {
    rmd_output <- names(rmd_output)[1]
  }
  if (rmd_output == "pdf_document") {
    return("latex")
  } else if (rmd_output %in% c("html_document", "html_vignette")) {
    return("html")
  } else if (rmd_output != "") {
    stop("Unsupported rmarkdown output format:", rmd_output)
  }
  # No rmarkdown, let's try with knitr:
  format <- knitr::opts_knit$get("out.format")
  if (format %in% c("html", "markdown")) {
    return("html")
  } else if (format %in% c("latex")) {
    return("latex")
  } else {
    stop("Format not supported!")
  }
}

guess_output_format <- function() {
  if (knitr::is_html_output()) {
    return("html")
  } else if (knitr::is_latex_output()) {
    return("latex")
  } else {
    return("unsupported")
 }
}