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Let's say I have an iOS app on the app store. Anyone can download and use it, but I would like to restrict the app from granting access to certain features to a select set of people I can personally vouch for. So, for example, to get access, the app send email to me, you have to convince me I know you, and if you do, I send you back some kind of token string which you can enter into the app. However, I'd like for that token to not be shareable, and to be locked to that device. Is there any kind of persistent ID associated with a device that I can use to tie the token I grant to that persistent ID? Or can someone suggest a way that once I trust a user, I can give them a token which will cannot be shared to anyone else? Also, does anyone know if restricting access to app features in this way is any kind of issue with regards to the app review process? The app itself is free, and there are no in-app purchases. I simply don't want certain features of the app (which end up sending push notifications) to get abused.

I'm brand new to Metal. I've googled, but can't get the right answer to come up. (Thanks, unhelpful ChatGPT generated answers polluting everything, but I digress...) Ultimately, I'm trying to figure out how to use Metal to render 3D DICOM data on iOS specifically. If you're not familiar with DICOM, let's just say I've got a whole stack of CT image slices. Or to get really simple, I've got a cube of voxel values with differing values at each voxel coordinate. Where do I even start in Metal to render something like this? (I was trying to get the VTK toolkit compiled for iOS, which uses OpenGL, but that appears to be a dead end. And besides, Metal is supposed to be so much better.) Thanks for any tips/leads/suggestions/general pointers.

In Xcode 7.2 (and possibly earlier versions of xcode 7.3, though I can't swear to it) it seems like "local" project results (e.g. files in my project) were favored by being put at the top of the completion list. For example, if I had the file "DirectoryViewController.swift" then typing "dire" into the open quickly search box would put my local file at the top, and system stuff like "dirent.h" etc. at the bottom.Now in Xcode 7.3 I find that Open Quickly is swamping me with results that come from stuff used by my project (e.g. names of public variables in swift classes from Foundation or UIKit) rather than stuff that I defined in my project (my own file names/public methods). Everything is being found, but local results no longer appear at the top.Is this intentional? Any chance the order could revert to what it was? A preference?Since there's far more global stuff (that one didn't write) than local stuff, it's very disconcerting that open quickly has become much less useful to me (i have to type many more characters to get what i want now near the top of the list) than it was in previous versions.any suggestions welcome (as are any fixes planned!)

I have a table (i.e. "List") with a large number of rows. (Say 1000. Say 10,000. Who knows.). The rows show images which are loaded from a remote server. The images are fetched lazily, so it is highly likely that if one scrolls fast enough, any given row of the table may display not the actual image, but a placeholder until the image is available.Prior to SwiftUI, the way I would do this is have a model backend which, when it loads an image, sends out a "signal" that an image with path P (i.e. some string identifying the image) is ready. The UITableViewController would have kept a map that says for any existing cell, what image that cell cares about. If the UITableViewController sees that an image that some existing cell cares about has been modified, it would reload JUST THAT ROW (updating a placeholder image, or switching out an activity spinner to the actual image).I believe in SwiftUI that I also want to be that performant: if the backend finishes loading an image, I only to update the row for that image. The way I'm doing this now is making a large number of very small BindableObject instances, and having each row hang onto that instance with an @ObjectBindingproperty wrapper. When an image finishes loading, I grab the bindable object corresponding to that image and make its didChange() variable fire.This seems to work OK, but (1) Each of these small bindable object instances has to be a class, not a struct. (2) So we're creating a lot of PassthroughSubject objects.Is this really the right way to get fine-grain notification? Would it/does it scale? Is there something better? I mean, I love how easy it is to do, and OMG, it's a lot simpler, bookkeeping wise than what I had before, and for sure, it doesn't even try to redraw anything that's way offscreen if you update the data, but want to make sure this is right.