regex.matches 方法匹配和计数错误

Question

In a TextView the user can insert text and images, like a notes. To save the whole TextView content in the database (Realm), I replaced the image itself for a pattern "[image]imageName[/image]", so when I load back this data to the TextView, I want to replace back this pattern for the images. I made this function:

let attributedString = NSMutableAttributedString(string: txtNote.text)

        let range = NSRange(location: 0, length: attributedString.string.utf16.count)
        let regex = NSRegularExpression("[image](.*?)[/image]")

        for match in regex.matches(in: attributedString.string, options: [], range: range) {
            if let rangeForImageName = Range(match.range(at: 1), in: attributedString.string){

                let imageName = String(attributedString.string[rangeForImageName])

                if let image = loadImage(named: imageName) {

                    let attachment = NSTextAttachment()
                    attachment.image = image
                    let oldWidth = attachment.image!.size.width;
                    let scaleFactor = (oldWidth / (txtNote.frame.size.width - 10))

                    attachment.image = UIImage(cgImage: attachment.image!.cgImage!, scale: scaleFactor, orientation: .up)

                    let attString = NSAttributedString(attachment: attachment)

                    txtNote.textStorage.insert(attString, at: txtNote.selectedRange.location)
                } else {
                    print("Image not found")
                }
            }
        }

I also have this extension to avoid a try catch in the function above:

extension NSRegularExpression {
    convenience init(_ pattern: String) {
        do {
            try self.init(pattern: pattern)
        } catch {
            preconditionFailure("Illegal regular expression: \(pattern).")
        }
    }
}

The example that I'm running, the content on attributedString:

Like Gorillaz :D
[image]4397ACA6-ADDC-4977-8D67-9FF44F10384A.jpeg[/image]

[image]9BE22CA8-9C6C-4FF9-B46F-D8AF33703061.jpeg[/image]

Etc.{
}

It should be 2 matches, and the image names should be: "4397ACA6-ADDC-4977-8D67-9FF44F10384A.jpeg" and "9BE22CA8-9C6C-4FF9-B46F-D8AF33703061.jpeg".

But my function is returning 14 matches and the image names like: "k", "ll", "", "]4397ACA6-ADDC-4977-8D67-9FF44F10384A.jp", "[", etc.

Any idea abou what I'm doing wrong? I've been research for some error like this unsuccessfully all day long.

Answer 1

The [image] and [/image] form character classes that match single chars, the former matching i , m , a , g or e and the latter also matching / .

If you want to treat a part of a regex as a literal substring, you may "quote" it with \\Q...\\E operators:

let regex = NSRegularExpression("\\Q[image]\\E(.*?)\\Q[/image]\\E")

If you are sure what you are doing, escape the brackets manually, "\\\\[image\\\\](.*?)\\\\[/image\\\\]" .

See Regular Expression Metacharacters table:

\\Q Quotes all following characters until \\E .
\\E Terminates a \\Q ... \\E quoted sequence.

"Quotes" means "adds backslashes before the special chars to make them match as literal chars" here.