Collapse multiple columns into one column based on values in R

I have data.frame df1:

 df1 <- data.frame(apple = c('0', '0', '0', '1', '0', '1', '0', '0', '0', '1'),
      banana = c('1', '0', '0', '0', '1', '0', '1', '0', '0', '0'),
      cherry = c('0', '1', '0', '0', '0', '0', '0', '1', '0', '0'),
      date = c('0', '0', '1', '0', '0', '0', '0', '0', '1', '0'))
 rownames(df1) <- c('one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten')

How can I substitute all ‘ones’ in each column with the column name and then collapse the column into one new column? Expected result is df2:

 df2 <- data.frame(fruit = c('banana', 'cherry', 'date', 'apple', 'banana', 
      'apple', 'banana', 'cherry', 'date', 'apple'))
 rownames(df2) <- c('one', 'two', 'three', 'four', 'five', 
      'six', 'seven', 'eight', 'nine', 'ten')

I found the second step here (r collapsing data from multiple columns into one) but I don’t quite get there yet.

>Solution :

Here is tidyverse way using transmute and unite:

library(dplyr)
library(tidyr)

df1 %>%
  transmute(across(apple:date, ~case_when(. == 1 ~ cur_column()), .names = 'new_{col}')) %>% 
  unite(fruit, starts_with('new'), na.rm = TRUE, sep = ' ')

       fruit
one   banana
two   cherry
three   date
four   apple
five  banana
six    apple
seven banana
eight cherry
nine    date
ten    apple