Replicating convenience implementations in Swift

Question

I am attempting to understand the following code and how you would convert it to Swift. Specifically, I understand this adds an instance method you can call on an instance of CIImage. My question is, how you can do the same thing in a Swift class?

This code is taken from AAPLAssetViewController.m in Apple's example app using the Photos framework.

@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

Call it like so:

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

Have a look at Swift Extensions. – Sebastian Jan 24 '15 at 19:50 — Sebastian, Jan 24 '15 at 19:50

score 0 · Accepted Answer · answered Jan 24 '15 at 20:08

From The Swift Programming Language - Extensions:

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

Replicating convenience implementations in Swift

1 Answers1