在 Swift 中复制便捷实现

Question

我试图理解以下代码以及如何将其转换为 Swift。具体来说，我知道这会添加一个实例方法，您可以在 CIImage 的实例上调用它。我的问题是，如何在 Swift class?

中做同样的事情

此代码取自 AAPLAssetViewController.m Apple 使用照片框架的示例应用程序。

@implementation CIImage (Convenience)
- (NSData *)aapl_jpegRepresentationWithCompressionQuality:(CGFloat)compressionQuality {
    static CIContext *ciContext = nil;
    if (!ciContext) {
        EAGLContext *eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
        ciContext = [CIContext contextWithEAGLContext:eaglContext];
    }
    CGImageRef outputImageRef = [ciContext createCGImage:self fromRect:[self extent]];
    UIImage *uiImage = [[UIImage alloc] initWithCGImage:outputImageRef scale:1.0 orientation:UIImageOrientationUp];
    if (outputImageRef) {
        CGImageRelease(outputImageRef);
    }
    NSData *jpegRepresentation = UIImageJPEGRepresentation(uiImage, compressionQuality);
    return jpegRepresentation;
}
@end

这样称呼它：

NSData *jpegData = [myCIImage aapl_jpegRepresentationWithCompressionQuality:0.9f];

Answer 1

来自Swift编程语言 - 扩展：

Extensions add new functionality to an existing class, structure, or enumeration type. (...) Extensions are similar to categories in Objective-C.

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Extensions.html

在 Swift 中复制便捷实现

Replicating convenience implementations in Swift

ios

objective-c

swift

instance-methods

convenience-methods