Question 66708 in IOS Swift Question posted in
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Why do I have to remove percent encoding twice for an encoded string? – Ios swift

This is my simple extension:

extension String {
    var urlDecoded: String? {
        replacingOccurrences(of: "+", with: "%20").removingPercentEncoding
    }
}

And here is my string:

let string = "https%253A%252F%252Fplz.pl"

After I call

let firstDecoded = string.urlDecoded

// "https%3A%2F%2Fplz.pl"

let secondDecoded = string.urlDecoded?.urlDecoded

// "https://plz.pl"

Why do I have to call it twice? How can I do it correctly and quickly?

Tags:

2

Answers


  1. 0

    Because the input is encoded twice.

    %253A: %25 is an encoded % meaning it results in %3A after the first decoding and : after the second decoding.

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  2. 0

    Why do you have to decode it twice? Because it’s been encoded twice.

    The ASCII code point for the percent symbol is 0x25. So %25 in an encoded URL encodes a percent symbol. Thus:

    https%253A%252F%252Fplz.pl
     └┬┘  └┬┘  └┬┘
https % 3A % 2F % 2Fplz.pl
      └┬─┘ └┬─┘ └┬─┘
https  :    /    /  plz.pl
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