如何避免R自动将日期转换为数字？

Question

How to avoid R converting dates to numeric in a for loop? This is related to this question that shows the same behavior for mapply disabling mapply automatically converting Dates to numeric

date <- c('2008-02-20','2009-10-05')
date <- as.Date(date, format = '%Y-%m-%d')
date
[1] "2008-02-20" "2009-10-05"
for (i in date) print(i)
[1] 13929
[1] 14522

disabling mapply automatically converting Dates to numeric

Edit

I have reopened this question since the duplicate Looping over a datetime object results in a numeric iterator asks why R loops convert date and datetime objects to numeric, this question asks how to avoid that behavior. And the answer is to the point solving the problem, unlike the accepted and other answers in the duplicate, that correctly answer that other question.

Answer 1

The for loop coerces the sequence to vector, unless it is vector, list, or some other things. date is not a vector, and there is no such thing as vector of dates. So you need as.list to protect it from coercion to vector:

for (d in as.list(date)) print(d)