On Mon, May 2, 2016, at 11:59 AM, Alex Zavatone wrote:
> That alone should give you pause.
>
> And I was trying to decipher how their code ended up transferring values
> from my object to a method that appears after a custom constructed alert.
>
> This alert is simply a few views and a few buttons. No UIAlertView or
> UIAlertController is used.
>
> What I found that shocked ad horrified me was that the object that was
> needed was being passed by adding it to the layer of the button by using
> an arbitrary key using KVC setValue: forKey: to an arbitrary key.
>
> First, I was rather confused since I had created an accessor for this
> value off of a unique key, so this level of strangeness didn't need to be
> done, but secondly I had no idea that this was even possible, or even if
> it was a good idea.
>
> The code looked something close to this:
>
> UIButton *someButton = [UIButton buttonWithType:UIButtonTypeCustom];
> someButton.tag = 1;
> [[someButton layer] setValue: someImportantObject
> forKey:@"someArbitraryKey"];
>
> And later on, when the button was tapped, they would get the object like
> so:
>
> switch ([sender tag]) { // That button
> case 1:
> {
> NSMutableDictionary *someImportantObject = [[sender
> layer]valueForKey:@"someArbitraryKey"];
> [self doStuffWith: someImportantObject];
> break;
> }
>
>
> I had no idea that using KVC that something as arbitrary as this was even
> possible - let alone if it is a good idea.
>
> For it being a good idea, it's obscure as can be, so no. But does KVC
> allow you to be as arbitrary as that with *any* object (in this case, an
> NSDictionary) to another that originates from an NSObject with NSCoding
> protocols?
No. This is a Core Animation-only extension to Key-Value Coding:
<https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/CoreAnimation_guide/Key-ValueCodingExtensions/Key-ValueCodingExtensions.html>
--Kyle Sluder
>
> I was looking around to see how the NSKeyValueCoding protocols are
> adopted into NSObject and therein into a UILayer and I couldn't find
> where this happens. Where does this happen?
>
> Also, though this can be done, it seems really really really really
> sketchy. Is it a valid approach - to use KVC to add arbitrary properties
> to any old NSObject or are there unexpected implications to be expected?
>
> Thanks in advance. My mind is sufficiently warped enough from 1.
> thinking WHY someone would do this, 2. thinking it would be a good idea
> and 3. adding it as relied upon functionality in a shipping project.
>
> The never ending list of surprises in this code give me PTSD.
>
> Cheers and thanks,
> Alex Zavatone
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