How to convert an array of tuples to a string?

Question

I'm reading from a file with the following data:

-LX-A7q4_8kFE4I_-iip,1
-LWyCOhwO_lUwMt-dOOa,1
-LWwVCZL5sfQYd4WtSHw,1

Each row is separated by "\n", and each element is separated by a comma.

I am able to read the file, put the contents into an array, with the correct rows and columns.

I am then able to filter the array to remove the row I want. Finally, I want to write the array back to the file in the same format. The code I have is as follows:

// This filters the array and gets me the rows I want.  
func writeToFile() {          
    let filteredMessageID = result.filter { $0.messageID != nominationKeyForReadStatus }
    //This is my attempt at converting the array to a string, before I try writing the string back to the file.  
    let filteredMessageIDJoinedString = filteredMessageID.joined(separator:"\n")
}

This last bit of code is clearly wrong, as my array, returned after filtering as filteredMessageID is as follows:

// ▿ 2 elements
  ▿ 0 : 2 elements
    - messageID : "-LWyCOhwO_lUwMt-dOOa"
    - readStatus : "1"
  ▿ 1 : 2 elements
    - messageID : "-LWwVCZL5sfQYd4WtSHw"
    - readStatus : "1"

How do I convert filteredMessageID back to a string that looks like this?

"-LWyCOhwO_lUwMt-dOOa,1\n-LWwVCZL5sfQYd4WtSHw,1"

Thanks in advance!

Sweeper · Accepted Answer · 2019-01-27 09:29:47Z

1

You need a map before the joined to transform each of the tuples to a String:

let filteredMessageIDJoinedString = filteredMessageID
    .map{ "\($0.messageID),\($0.readStatus)" } // notice the comma in the middle
    .joined(separator:"\n")

Your format looks like CSV. You can find out how to read and write CSV with Swift here.

edited Jan 27, 2019 at 9:29

answered Jan 27, 2019 at 9:28

Sweeper

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2 Comments

Sweeper Over a year ago

@nm1213 Is there a problem with my answer?

nm1213 Over a year ago

Sweeper, not at all. It worked perfectly. I’m still working on the function to complete it, but your solution is exactly the right approach.

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