How to write a text file consisting of double values into an array in Swift

Question

Does anyone know how it is possible in Swift to read the contents of a text file into an array? I'm having problems with the data type conversion here and so far I can't find a way to save a file that consists of double values into an array. In addition, the values are only separated by line breaks. So a field of an array would have to be a single row. How can I write an automated query that can read a complete text file?

The dataset in the text file looks like this:

0.123123
0.123232
0.344564
-0.123213 ... and so on

Check if this helps: stackoverflow.com/questions/29217554/… — algo_user
– algo_user, Commented Oct 22, 2020 at 17:44
Does this answer your question? Swift Text File To Array of Strings — Joakim Danielson
– Joakim Danielson, Commented Oct 22, 2020 at 18:37
Sorry, but these two cases do not deal with the problem of data types. In these cases, the text file is divided into strings. However, I need these as doubles. — Hannes Broschk
– Hannes Broschk, Commented Jan 29, 2021 at 11:13

Leo Dabus · Accepted Answer · 2020-10-22 19:00:32Z

2

You can split your string where separator is new line and then compactmap initialising the substrings into Double:

let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
    .appendingPathComponent("file.txt")
// or if the file is located in you bundle directory
// let url = Bundle.main.url(forResource: "file", withExtension: "txt")!
do {
    let txt = try String(contentsOf: url)
    let numbers = txt.split(whereSeparator: \.isNewline)
                      .compactMap(Double.init) // [0.123123, 0.123232, 0.344564, -0.123213]
} catch {
    print(error)
}

This assumes there is no spaces before or after your numbers. If you need to make sure the double initializer will not fail in those cases you can trim them before initialising your numbers:

let numbers = txt.split(whereSeparator: \.isNewline)
    .map { $0.trimmingCharacters(in: .whitespaces) }
    .compactMap(Double.init)

edited Oct 22, 2020 at 19:00

answered Oct 22, 2020 at 18:43

Leo Dabus

237k61 gold badges512 silver badges624 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to write a text file consisting of double values into an array in Swift

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related