如何從像「rgb（0,0,0）」這樣的字符串中創建UIColor？

Question

我有一個像「rgb（0,0,0）」格式的服務器的字符串，應該在某些UI元素上使用。

的主要問題是各種顏色，如「RGB（20,120,4）」等

有沒有一種方法來分析它像UIColor(red: 0, green: 0, blue: 0, alpha: 1)？

Answer 1

有這麼多的可能的解決方案！下面是一個使用 NSScanner：

extension UIColor { 
    convenience init?(rgbString : String) { 
     var red = 0.0 
     var green = 0.0 
     var blue = 0.0 

     let scanner = NSScanner(string : rgbString) 
     guard scanner.scanString("rgb(", intoString: nil) 
      && scanner.scanDouble(&red) 
      && scanner.scanString(",", intoString: nil) 
      && scanner.scanDouble(&green) 
      && scanner.scanString(",", intoString: nil) 
      && scanner.scanDouble(&blue) 
      && scanner.scanString(")", intoString: nil) else { 
       return nil 
     } 
     self.init(red: CGFloat(red/255.0), green: CGFloat(green/255.0), blue: CGFloat(blue/255.0), alpha: 1.0) 
    } 
} 

用例：

if let col = UIColor(rgbString: "rgb(20,120.5, 4)") { 
    print(col) 
} else { 
    print("invalid color specification") 
} 

更新斯威夫特3/4：

extension UIColor { 
    convenience init?(rgbString: String) { 
     var red = 0.0 
     var green = 0.0 
     var blue = 0.0 

     let scanner = Scanner(string: rgbString) 
     guard scanner.scanString("rgb(", into: nil) 
      && scanner.scanDouble(&red) 
      && scanner.scanString(",", into: nil) 
      && scanner.scanDouble(&green) 
      && scanner.scanString(",", into: nil) 
      && scanner.scanDouble(&blue) 
      && scanner.scanString(")", into: nil) else { 
       return nil 
     } 
     self.init(red: CGFloat(red/255.0), green: CGFloat(green/255.0), blue: CGFloat(blue/255.0), alpha: 1.0) 
    } 
} 

Answer 2

你可以試試這個。

import UIKit 

let string1 = "rgb(25.00,100.0,100)" 

let indexToRemoveTheLast = string1.endIndex.advancedBy(-1) 
let substring1 = string1.substringToIndex(indexToRemoveTheLast) 
let indexToRemoveTheFirst = string1.startIndex.advancedBy(4) 
let substring2 = substring1.substringFromIndex(indexToRemoveTheFirst) 

var colorsString = substring2.characters.split{$0 == ","}.map(String.init) 
let red = (Float(colorsString[0])!)/255 
let green = (Float(colorsString[1])!)/255 
let blue = (Float(colorsString[2])!)/255 

let myColor = UIColor(red: CGFloat(red), green: CGFloat(green), blue: CGFloat(blue), alpha: 1) 

的結果在這裏：

Answer 3

這裏是將您的字符串轉換爲UIColor的方法。可能有正則表達式更好的解決方案，但我在正則表達式中很糟糕。

func colorFromString(colorString: String) -> UIColor? { 
    // strip down rgb and parenthesis 
    let combinedCharacterSet = NSMutableCharacterSet.letterCharacterSet() 
    combinedCharacterSet.addCharactersInString("()") 

    let trimmedString = colorString.stringByTrimmingCharactersInSet(combinedCharacterSet) 
    let rgbValueStrings = trimmedString.componentsSeparatedByString(",") 

    if rgbValueStrings.count != 3 { 
     return nil 
    } 

    if let r = Double(rgbValueStrings[0]) where r >= 0 && r <= 255, 
     let g = Double(rgbValueStrings[1]) where g >= 0 && g <= 255, 
     let b = Double(rgbValueStrings[2]) where b >= 0 && b <= 255 { 
     return UIColor(red: CGFloat(r/255), green: CGFloat(g/255), blue: CGFloat(b/255), alpha: 1.0) 
    } else { 
     return nil 
    } 
} 

和操場可以downloaded here