FormattableAttributedString.swift

import UIKit


class FormattableAttributedString {
    
    /* class */ let formatPattern = NSRegularExpression(pattern: "\\{(\\w+)\\}", options: nil, error: nil)!
    
    var formatString : NSMutableAttributedString
    var formatSpecifiers : [String: NSRange] = [:]
    
    init(_ string: String) {
        self.formatString = NSMutableAttributedString(string: string)
        let str = string as NSString
        let range = NSMakeRange(0, str.length)
        
        self.formatPattern.enumerateMatchesInString(str, options: nil, range: range, usingBlock: {
            (result, flags, stop) -> Void in
            let specifier = str.substringWithRange( result.rangeAtIndex( 1 ) )
            self.formatSpecifiers[specifier] = result.range
        })
    }
    
    
    func setAttributes(attributes: [NSObject: AnyObject], forSpecifier: String) {
        if let range = self.formatSpecifiers[forSpecifier] {
            self.formatString.setAttributes(attributes, range: range)
        }
    }
    
    
    func format (mapping: [String:String]) -> NSMutableAttributedString? {
        
        if mapping.isEmpty {
            return nil
        }
        
        var nongivenSpecifier = false
        
        for specifier in self.formatSpecifiers.keys {
            if let target = mapping[specifier] {
                continue
            } else {
                nongivenSpecifier = true
                break
            }
        }
        
        if nongivenSpecifier {
            return nil
        }
        
        
        var result = NSMutableAttributedString(attributedString: self.formatString)
        
        for (specifier, range) in self.formatSpecifiers {
            result.replaceCharactersInRange(range, withString: mapping[specifier]!)
        }
        
        return result
    }
}




let redColorAttribute = [NSForegroundColorAttributeName : UIColor.redColor()]


let string = FormattableAttributedString("Add {tagname} tag")

string.setAttributes(redColorAttribute, forSpecifier: "tagname")

string.format(["tagname" : "FooBar"])!
string.format(["tagname" : "Jeena"])!



let complexString = FormattableAttributedString("Die {star} scheint mir aus dem {bodypart}, du {adressed}")

for tag in ["star", "bodypart", "adressed"] {
    complexString.setAttributes(redColorAttribute, forSpecifier: tag)
}

complexString.format([
    "star"          : "Sonne",
    "bodypart"      : "Arsche",
    "adressed"      : "Depp",
    "unused"        : "unused"
])!




if let x = string.format(["eins" : "zwei"]) {
    println("huch?")
} else {
    println("falscher Tag")
}