Select first or last object from id<NSFastEnumeration>

Question

I found this code in our project and it just feels like the wrong way to do what it seems to be doing

id<NSFastEnumeration> results = [info objectForKey: ZBarReaderControllerResults];
ZBarSymbol *symbol = nil;
for (symbol in results) {
    // this just selects the first symbol in the results
}

Presumably it actually doesn't select the first symbol - instead it selects the last one!

But there must be a better way. I don't quite know what

[info objectForKey: ZBarReaderControllerResults]

returns, but I'm not too bothered either. Is there a way that I can do the above code without having to loop through all possible results?

Answer 1

ZBarSDK is the only place I've ever seen NSFastEnumeration. I don't know a whole lot about it, nor do I know exactly why ZBarSDK was designed to be used in this way.

NSFastEnumeration isn't any faster than using a forin loop. It is faster than a regular for or while (or do-while) loop, but not faster than a forin.

In a forin loop, we're using regular Objective-C collections, and NSArray has a firstObject and lastObject.

But if the real question is (and should be) how do I improve this code (more than just specifically grabbing a single object out of an NSFastEnumeration), then the answer is to use AVCaptureMetadataOutput (official documentation), which was introduced in iOS7.

ZBarSDK has an iOS7 memory leak. Also, I don't know about compiled on-device size, but when I removed it from my project, it saved about 1.4mb from the project size.

Meanwhile, AVCaptureMetadataOutput has many advantages over ZBarSDK.

• It's slightly easier to use... and it's simple to use if you're already familiar with video capture in iOS.
• It leaves a smaller footprint in terms of storage space your app takes up on a device.
• Even without ZBarSDK's memory leak, AVCaptureMetadataOutput has a smaller memory footprint.
• AVCaptureMetadataOutput seems to scan barcodes faster and a farther distances than what I could manage with ZBarSDK.
• ZBarSDK doesn't support 64-bit processors at all. AVCaptureMetadataOutput however does.