Question

我需要从show方法中恢复隐式用于调用show的调用的表达式，但这仅适用于显式show show：

> setClass("test", representation(a="character"))
> setMethod("show", "test", function(object) cat(deparse(substitute(object))))
[1] "show"
> show(new("test"))    # explicit call: as expected
new("test")
> new("test")          # implicit: not so much...
<S4 object of class structure("test", package = ".GlobalEnv")>

打印和S3对象似乎有类似的问题，但我对这里的S4版本更感兴趣。有办法解决这个问题吗？我用sys.calls查看了调用堆栈，但没有使用原始表达式记录的调用，这表明这可能太低而无法轻易解决。

Answer 1

> showDefault
function (object, oldMethods = TRUE) 
{
    clDef <- getClass(cl <- class(object), .Force = TRUE)
    cl <- classLabel(cl)
    if (!is.null(clDef) && isS4(object) && is.na(match(clDef@className, 
        .BasicClasses))) {
        cat("An object of class ", cl, "\n", sep = "")
        slots <- slotNames(clDef)
        dataSlot <- .dataSlot(slots)
        if (length(dataSlot) > 0) {
            dataPart <- slot(object, dataSlot)
            show(dataPart)
            slots <- slots[is.na(match(slots, dataSlot))]
        }
        else if (length(slots) == 0L) 
            show(unclass(object))
        for (what in slots) {
            if (identical(what, ".Data")) 
                next
            cat("Slot \"", what, "\":\n", sep = "")
            print(slot(object, what))
            cat("\n")
        }
    }
    else print(object, useS4 = FALSE)
    invisible()
}
<bytecode: 0x11c228000>
<environment: namespace:methods>

从隐含的“show”调用替换

1 个答案: