Replace one regex match with another and vice versa

Question

I need to replace in string foo bar foo bar bar foo all foo to bar and all bar to foo. So the result should look like bar foo bar foo foo bar.

I have tried this way:

library(stringr)

my_str <- "foo bar foo bar bar foo"
rslt <- str_replace_all(my_str, c("foo", "bar"), c("bar", "foo"))

print(rslt)

but instead I got "bar bar bar bar bar bar" "foo foo foo foo foo foo".

Question: How to correct my code so I get bar foo bar foo foo bar?

Answer 1

Using str_replace_all multiple replacements and moving the first match to a temporary value.

library(stringr)

str_replace_all(my_str, c("foo" = "tmp", "bar" = "foo", "tmp" = "bar"))

[1] "bar foo bar foo foo bar"

Answer 2

No real reason to do this unless you're unable to install extra packages, but just for fun here's a base R solution (following the "tmp" replacement method in @manotheshark's answer):

Reduce(
  function(prev, x) gsub(x[1], x[2], prev),
  list(c('foo', 'tmp'), c('bar', 'foo'), c('tmp', 'bar')),
  my_str)
# [1] "bar foo bar foo foo bar"