如何在NSMutableAttributedString中设置对齐方式iOS Swift 3

Question

I want to change alignment of my html in iOS Swift 3 Xcode 8.3 .
Every things works correctly but i do not know about alignment .
My code like this:

extension String {
    func htmlAttributedString() -> NSAttributedString? {
        guard let data = self.data(using: String.Encoding.utf16, allowLossyConversion: false) else { return nil }

        let style = NSMutableParagraphStyle()
        style.alignment = NSTextAlignment.center


        guard let html = try? NSMutableAttributedString(
            data: data,
            options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,NSTextAlignment:.center],
            documentAttributes:nil) else { return nil }


        return html
    }
}

Answer 1

The reason of getting the error is that options parameter is a dictionary of type: [String : Any] , passing NSDocumentTypeDocumentAttribute (String) and NSTextAlignment (Int) is illegal (dictionaries are strongly typed).

The solution would be to use NSMutableParagraphStyle and add it as an option; You are already declared one and set its alignment to .center , but you are not using it!

You should add it with NSParagraphStyleAttributeName key (instead of NSTextAlignment ), as follows:

extension String {
    func htmlAttributedString() -> NSAttributedString? {
        guard let data = self.data(using: String.Encoding.utf16, allowLossyConversion: false) else { return nil }

        let style = NSMutableParagraphStyle()
        style.alignment = NSTextAlignment.center

        guard let html = try? NSMutableAttributedString(
            data: data,
            options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
                      NSParagraphStyleAttributeName: style],

            documentAttributes:nil) else { return nil }

        return html
    }
}

Note that NSParagraphStyleAttributeName data type is String, which means that the data type of the options dictionary would be -legally- [String : Any] .