如何在Swift中调用Objective-C类别方法 [英] How to call an Objective-C category method in Swift

问题描述

你如何在Swift中调用这样的Objective-C类别方法？

How would you call an Objective-C category method like this in Swift?

+(UIColor*)colorWithHexString:(NSString*)hex alpha:(float)alpha;

推荐答案

编译器自动查找常见的ObjC命名模式和替代品快速模式取而代之。一个ObjC类方法返回一个类的实例（并以某种方式命名，看起来像）被转换为Swift便利初始化器。

The compiler automatically looks for common ObjC naming patterns and substitutes Swift patterns in their place. An ObjC class method that returns an instance of the class (and is named a certain way, it looks like) gets turned into a Swift convenience initializer.

如果你有ObjC方法（由自定义类别定义）：

If you have the ObjC method (defined by a custom category):

 + (UIColor *)colorWithHexString:(NSString *)hex alpha:(float)alpha;

编译器生成Swift声明：

The compiler generates the Swift declaration:

convenience init(hexString: String?, alpha: CFloat)

你这样称呼：

let color = UIColor(hexString: "#ffffff", alpha: 1.0)

---

在Swift 2.0或更高版本中，您可以使用 NS_SWIFT_NAME 宏使ObjC工厂方法与作为初始化程序的Swift的命名模式导入不匹配。例如：

---

And in Swift 2.0 or later, you can use the NS_SWIFT_NAME macro to make ObjC factory methods that don't match the naming pattern import to Swift as initializers. e.g.:

@interface UIColor(Hex)
+ (UIColor *)hexColorWithString:(NSString *)string
NS_SWIFT_NAME(init(hexString:));
@end

// imports as
extension UIColor {
    init(hexString: String)
}

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