blocks|key|2861505|text|您可以创建一个默认值为String的Color枚举：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2861506|+enum+Color:+String+{
+++case+red
+++case+blue
+++case+green

++++var+create:+UIColor+{
+++++++switch+self+{
++++++++++case+.red:
++++++++++++return+UIColor.red
++++++++case+.blue:
++++++++++++return+UIColor.blue
++++++++case+.green:
++++++++++++return+UIColor.green
+++++++}
++++}
++}|code-block|syntax|javascript|2861507|由于它的默认值为String，因此您可以使用字符串初始化枚举：|2861508|++guard+let+color+=+Color(rawValue:+"red")+else+{+"handle+invalid+color+error";+return+}+

+let+colorSelected+=+color.create+////+colorSelected+is+now+UIColor.red|2861509|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can create a Color enum that has a default value of String:

<pre><code> enum Color: String {
 case red
 case blue
 case green

 var create: UIColor {
 switch self {
 case .red:
 return UIColor.red
 case .blue:
 return UIColor.blue
 case .green:
 return UIColor.green
 }
 }
 }
</code></pre>

Since it has a default value of String you can initialize the enum with a string:

<pre><code> guard let color = Color(rawValue: "red") else { "handle invalid color error"; return } 

 let colorSelected = color.create //// colorSelected is now UIColor.red
</code></pre>

blocks|key|107408|text|您可以在Swift中编写类似于Objective-C代码的代码，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|107409|extension+UIColor+{
++++@objc(turquoiseColor)
++++public+class+var+turquoise:+UIColor+{+return+UIColorFromRGB(0x40E0D0)+}
}

extension+UIColor+{
++++@objc(mediumTurquoiseColor)
++++public+class+var+mediumTurquoise:+UIColor+{+return+UIColorFromRGB(0x48D1CC)+}
}

let+myColor:+UIColor+=+.turquoise

func+getColor(_+name:+String)+->+UIColor?+{
++++let+selector+=+Selector("\(name)Color")
++++if+UIColor.self.responds(to:+selector)+{
++++++++let+color+=+UIColor.self.perform(selector).takeUnretainedValue()
++++++++return+(color+as!+UIColor)
++++}+else+{
++++++++return+nil
++++}
}

var+name:+String+=+"turquoise"
if+let+color+=+getColor(name)+{
++++print(color)+//->UIExtendedSRGBColorSpace+0.25098+0.878431+0.815686+1
}+else+{
++++print("color+with+name:\(name)+is+unavailable")
}|code-block|syntax|javascript|107410|但是使用Selector似乎并不是那么迅速。|offset|length|style|CODE|107411|您可以简单地准备一个包含UIColors的字典：|107412|let+myColors:+[String:+UIColor]+=+[
++++"red":+.red,
++++"white":+.white,
++++//...
++++"turquoise":+UIColorFromRGB(0x40E0D0),
++++"mediumTurquoise":+UIColorFromRGB(0x48D1CC),
]
name+=+"mediumTurquoise"
if+let+color+=+myColors[name]+{
++++print(color)
}+else+{
++++print("color+with+name:\(name)+is+unavailable")
}|107413|或者，JustinM的回答是一个非常好的建议。|107414|entityMap^0|0|0|4|8|0|C|7|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@$I|10|J|11|K|L]]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

You can write something similar to your Objective-C code in Swift like this:

<pre><code>extension UIColor {
 @objc(turquoiseColor)
 public class var turquoise: UIColor { return UIColorFromRGB(0x40E0D0) }
}

extension UIColor {
 @objc(mediumTurquoiseColor)
 public class var mediumTurquoise: UIColor { return UIColorFromRGB(0x48D1CC) }
}

let myColor: UIColor = .turquoise

func getColor(_ name: String) -&gt; UIColor? {
 let selector = Selector("\(name)Color")
 if UIColor.self.responds(to: selector) {
 let color = UIColor.self.perform(selector).takeUnretainedValue()
 return (color as! UIColor)
 } else {
 return nil
 }
}

var name: String = "turquoise"
if let color = getColor(name) {
 print(color) //-&gt;UIExtendedSRGBColorSpace 0.25098 0.878431 0.815686 1
} else {
 print("color with name:\(name) is unavailable")
}
</code></pre>

But using <code>Selector</code> does not seem to be Swifty.

You can simply prepare a Dictionary containing <code>UIColor</code>s:

<pre><code>let myColors: [String: UIColor] = [
 "red": .red,
 "white": .white,
 //...
 "turquoise": UIColorFromRGB(0x40E0D0),
 "mediumTurquoise": UIColorFromRGB(0x48D1CC),
]
name = "mediumTurquoise"
if let color = myColors[name] {
 print(color)
} else {
 print("color with name:\(name) is unavailable")
}
</code></pre>

Or JustinM's answer is a very good suggestion.

blocks|key|107543|text|使用这个UIColor扩展，它有两种将RGBA字符串和十六进制字符串转换为UIColor的方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|107544|++++extension+UIColor+{


++++//Convert+RGBA+String+to+UIColor+object
++++//"rgbaString"+must+be+separated+by+space+"0.5+0.6+0.7+1.0"+50%25+of+Red+60%25+of+Green+70%25+of+Blue+Alpha+100%25
++++public+convenience+init?(rgbaString+:+String){
++++++++self.init(ciColor:+CIColor(string:+rgbaString))
++++}

++++//Convert+UIColor+to+RGBA+String
++++func+toRGBAString()->+String+{

++++++++var+r:+CGFloat+=+0
++++++++var+g:+CGFloat+=+0
++++++++var+b:+CGFloat+=+0
++++++++var+a:+CGFloat+=+0
++++++++self.getRed(&r,+green:+&g,+blue:+&b,+alpha:+&a)
++++++++return+"\(r)+\(g)+\(b)+\(a)"

++++}
++++//return+UIColor+from+Hexadecimal+Color+string
++++public+convenience+init?(hexString:+String)+{

++++++++++++let+r,+g,+b,+a:+CGFloat

++++++++++++if+hexString.hasPrefix("#")+{
++++++++++++++++let+start+=+hexString.index(hexString.startIndex,+offsetBy:+1)
++++++++++++++++let+hexColor+=+hexString.substring(from:+start)

++++++++++++++++if+hexColor.characters.count+==+8+{
++++++++++++++++++++let+scanner+=+Scanner(string:+hexColor)
++++++++++++++++++++var+hexNumber:+UInt64+=+0

++++++++++++++++++++if+scanner.scanHexInt64(&hexNumber)+{
++++++++++++++++++++++++r+=+CGFloat((hexNumber+&+0xff000000)+>>+24)+/+255
++++++++++++++++++++++++g+=+CGFloat((hexNumber+&+0x00ff0000)+>>+16)+/+255
++++++++++++++++++++++++b+=+CGFloat((hexNumber+&+0x0000ff00)+>>+8)+/+255
++++++++++++++++++++++++a+=+CGFloat(hexNumber+&+0x000000ff)+/+255
++++++++++++++++++++++++self.init(red:+r,+green:+g,+blue:+b,+alpha:+a)
++++++++++++++++++++++++return
++++++++++++++++++++}
++++++++++++++++}
++++++++++++}

++++++++++++return+nil
++++++++}
++++//+Convert+UIColor+to+Hexadecimal+String
++++func+toHexString()+->+String+{
++++++++var+r:+CGFloat+=+0
++++++++var+g:+CGFloat+=+0
++++++++var+b:+CGFloat+=+0
++++++++var+a:+CGFloat+=+0
++++++++self.getRed(&r,+green:+&g,+blue:+&b,+alpha:+&a)
++++++++return+String(
++++++++++++format:+"%2502X%2502X%2502X",
++++++++++++Int(r+*+0xff),
++++++++++++Int(g+*+0xff),
++++++++++++Int(b+*+0xff)
++++++++)
++++}
}|code-block|syntax|javascript|107545|entityMap^0|4|7|11|7|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

Use this extension of <code>UIColor</code> which have two methods for converting RGBA string and Hexadecimal String to <code>UIColor</code>

<pre><code> extension UIColor {


 //Convert RGBA String to UIColor object
 //"rgbaString" must be separated by space "0.5 0.6 0.7 1.0" 50% of Red 60% of Green 70% of Blue Alpha 100%
 public convenience init?(rgbaString : String){
 self.init(ciColor: CIColor(string: rgbaString))
 }

 //Convert UIColor to RGBA String
 func toRGBAString()-&gt; String {

 var r: CGFloat = 0
 var g: CGFloat = 0
 var b: CGFloat = 0
 var a: CGFloat = 0
 self.getRed(&amp;r, green: &amp;g, blue: &amp;b, alpha: &amp;a)
 return "\(r) \(g) \(b) \(a)"

 }
 //return UIColor from Hexadecimal Color string
 public convenience init?(hexString: String) {

 let r, g, b, a: CGFloat

 if hexString.hasPrefix("#") {
 let start = hexString.index(hexString.startIndex, offsetBy: 1)
 let hexColor = hexString.substring(from: start)

 if hexColor.characters.count == 8 {
 let scanner = Scanner(string: hexColor)
 var hexNumber: UInt64 = 0

 if scanner.scanHexInt64(&amp;hexNumber) {
 r = CGFloat((hexNumber &amp; 0xff000000) &gt;&gt; 24) / 255
 g = CGFloat((hexNumber &amp; 0x00ff0000) &gt;&gt; 16) / 255
 b = CGFloat((hexNumber &amp; 0x0000ff00) &gt;&gt; 8) / 255
 a = CGFloat(hexNumber &amp; 0x000000ff) / 255
 self.init(red: r, green: g, blue: b, alpha: a)
 return
 }
 }
 }

 return nil
 }
 // Convert UIColor to Hexadecimal String
 func toHexString() -&gt; String {
 var r: CGFloat = 0
 var g: CGFloat = 0
 var b: CGFloat = 0
 var a: CGFloat = 0
 self.getRed(&amp;r, green: &amp;g, blue: &amp;b, alpha: &amp;a)
 return String(
 format: "%02X%02X%02X",
 Int(r * 0xff),
 Int(g * 0xff),
 Int(b * 0xff)
 )
 }
}
</code></pre>

blocks|key|109963|text|从OOPer的答案中简化。我的情况是我没有颜色映射的集合。我必须直接从字符串中获取颜色。如果它不存在，请使用其他内容。下面是我的扩展：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|109964|import+UIKit

extension+UIColor+{+

++++static+func+colorWith(name:String)+->+UIColor?+{
++++++++let+selector+=+Selector("\(name)Color")
++++++++if+UIColor.self.responds(to:+selector)+{
++++++++++++let+color+=+UIColor.self.perform(selector).takeUnretainedValue()
++++++++++++return+(color+as?+UIColor)
++++++++}+else+{
++++++++++++return+nil
++++++++}
++++}
}|code-block|syntax|javascript|109965|用法：|109966|self.view.backgroundColor+=+UIColor.color(name:+"red")+??+.blue|109967|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Simplification from OOPer's answer. My situation is that I do not have a collection of colour mappings. I have to get the colour from string directly. If it does not exist, use something else. Here is my extension:

<pre><code>import UIKit

extension UIColor { 

 static func colorWith(name:String) -&gt; UIColor? {
 let selector = Selector("\(name)Color")
 if UIColor.self.responds(to: selector) {
 let color = UIColor.self.perform(selector).takeUnretainedValue()
 return (color as? UIColor)
 } else {
 return nil
 }
 }
}
</code></pre>

Usage: 

<pre><code>self.view.backgroundColor = UIColor.color(name: "red") ?? .blue
</code></pre>

I am trying to convert an existing program which uses a list of predefined colors from Objective-C to Swift.
The original code used Selector to extract a <code>UIColor</code> based on it name represented as a <code>NSString</code>

<pre><code>#define UIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue &amp; 0xFF0000) &gt;&gt; 16))/255.0 green:((float)((rgbValue &amp; 0xFF00) &gt;&gt; 8))/255.0 blue:((float)(rgbValue &amp; 0xFF))/255.0 alpha:1.0]

-(UIColor *)getColor:(NSString*)colorName
{
 SEL selColor = NSSelectorFromString(colorName);
 NSString *errorMessage = [NSString stringWithFormat:@"Invalid color name: %@ !!!", colorName];
 NSAssert([UIColor respondsToSelector:selColor] == YES, errorMessage);
 UIColor *mycolor = [UIColor performSelector:selColor];
 return mycolor;
}

+ (instancetype)turquoiseColor {
 return UIColorFromRGB(0x40E0D0);
}

+ (instancetype)mediumTurquoiseColor {
 return UIColorFromRGB(0x48D1CC);
}
</code></pre>

However, I have been unable to work out how to achieve the same functionality using Swift 3.0, or whether the use of Selector is even the best technique.

<pre><code>func UIColorFromRGB(_ rgbValue: UInt) -&gt; UIColor {
 return UIColor(
 red: CGFloat((rgbValue &amp; 0xFF0000) &gt;&gt; 16) / 255.0,
 green: CGFloat((rgbValue &amp; 0x00FF00) &gt;&gt; 8) / 255.0,
 blue: CGFloat(rgbValue &amp; 0x0000FF) / 255.0,
 alpha: CGFloat(1.0)
 )
}

extension UIColor {
 public class var turquoise: UIColor { return UIColorFromRGB(0x40E0D0) }
}

extension UIColor {
 public class var mediumTurquoise: UIColor { return UIColorFromRGB(0x48D1CC) }
}

let myColor: UIColor = .turquoise

let name: String = "turquoise"
let colorName = "UIColor.\(name)"
let selector: Selector = NSSelectorFromString(colorName)

let colorSelected: UIColor = UIColor.perform(selector!)
</code></pre>

<blockquote>
 Error: ! No 'perform' candidates produce the expected contextual result type 'UIColor'
</blockquote>

How to convert a String to UIColor in Swift 3.0?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试将一个使用预定义颜色列表的现有程序从Objective-C转换为Swift。原始代码使用选择器根据表示为NSString的名称提取UIColor#define UIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF000...

问如何在Swift 3.0中将字符串转换为UIColor？
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问如何在Swift 3.0中将字符串转换为UIColor？
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