How to get record before and after in forall loop powerapps

Question

I am trying to run a function that returns a table with a corresponding date index and date text. This is so that I can display the information in a tutorial screen. However, I am confused on how to access to the previous record. Here is my pseudocode:

ForAll( Tweets (sorted by crf1d_date_index),
        If(the record IS NOT the LAST record,
             If('crf1d_date_index' != 'crf1d_date_index' of the NEXT record,
                     { 
                           Step: crf1d_date_index, 
                           Text: crf1d_tweet_time 
                     }
               )
           )

        If(the record IS the LAST record,
             If('crf1d_date_index' != 'crf1d_date_index' of the PREVIOUS record),
                     { 
                           Step: crf1d_date_index, 
                           Text: crf1d_tweet_time 
                     }
               )

)

Answer 1

You can use the Sequence function to create a list of indices, and then use that list within ForAll to access your list of tweets, something along the lines of the expression below:

With(
  { myTweets, Tweets(sorted by crf1d_date_index) },
  ForAll(
    Sequence(CountRows(myTweets)),
    With(
      {
        tweet: Index(myTweets, Value),
        previousTweet: If(Value > 1, Index(myTweets, Value - 1)),
        nextTweet: If(Value < CountRows(myTweets), Index(myTweets, Value + 1))
      },
      If(
        Value < CountRows(myTweets),
        If(
          tweet.'crf1d_date_index' != nextTweet.'crf1d_date_index',
          { Step: crf1d_date_index, Text: crf1d_tweet_time }
        ),
        If(
          tweet.'crf1d_date_index' != previousTweet.'crf1d_date_index',
          { Step: crf1d_date_index, Text: crf1d_tweet_time }
        )
      )
    )
  )
)

Answer 2

Set(distinctTweets, AddColumns(
    GroupBy(Tweets, "crf1d_date_index", "Dates"),
    "tweet_time",
    First(Dates).tweet_time));

With({myTweets:SortByColumns(distinctTweets,"crf1d_date_index")},
    ForAll(Sequence(CountRows(myTweets)),
        With({tweet:Index(myTweets,Value)},
            If(true,
                {
                    Step:Value-1,
                    Text: tweet.tweet_time,
                    Image: SampleImage
                }, Blank()
            )
        )
    )
)