以下代码块取自chernan's sample REST queries将对参数列表应用FUN,但未提供“param_name”。这怎么可能?sapply()如何应用未定义(无默认)参数的函数
rcurl_request <- function(service_url, parameters) {
# Collapse all parameters into one string
all_parameters <- paste(
sapply(names(parameters),
FUN=function(param_name, parameters) {
paste(param_name, paste(parameters[[param_name]], collapse=','), collapse='', sep='=')
},
parameters),
collapse="&")
# Paste base URL and parameters
requested_url <- paste0(service_url, all_parameters)
# Encode URL (in case there would be any space character for instance)
requested_url <- URLencode(requested_url)
# Start request to service
response <- getURL(requested_url, .opts = list(ssl.verifypeer = FALSE))
return(response)
}