Does iOS lost most of the advantage of using dynamic frameworks?

Question

Does iOS lost most of the advantage of using dynamic frameworks?

• Since iOS will copy all the dynamic frameworks needed into the app bundle, it doesn't share dynamic frameworks between apps and save memory. Except for sharing memory with the main app and its extensions.

• App using dlOpen can not ship to App Store. Which means Apple disallow dynamic framework from being used officially.

• The old Apple document says dynamic frameworks save app launch time, but the new document says they don't. Is the old document outdated? Here is the comparision:

  • make the app launch faster and use less memory once it’s launched
  • Load fewer dynamic libraries. This can be one of the longest parts of an app’s total launch time. Apple recommends using only up to six non-system frameworks See if you can remove any of the dynamic libraries you’re using by replacing them with static versions or compiling their sources directly.

Does it mean if we use dynamic frameworks with dlOpen to load them later, it will be faster than static frameworks? Because the dynamic frameworks take some time to link in the begining, but they save more time in loading into memory. And loading time of static frameworks is greater then the linking time in dynamic frameworks. Is that true?

So it looks like there is none adavantage of using dynamic frameworks on iOS, right?

And how about on macOS and Linux? Do dynamic frameworks have any advantage? If so, how do they work?

Answer 1

You're correct in all of this. Non-system (i.e. not provided by Apple) dynamic libraries going to be less efficient in pretty much every way on iOS. They give you no space or memory savings, and they cost you at launch time.

The old Apple document you reference was almost entirely written before the iPhone. It's referring to late-loading libraries in Mac apps, which can help launch time.

On systems with shared libraries (or when using system libraries, which are shared on iOS), dynamic libraries save disk space, and can be shared between processes which saves memory and load time (because it's already loaded by some other process). But if you don't share the library, you can't really get any of those benefits. On systems that allow runtime loading of libraries (not iOS), dynamic libraries can delay the cost of loading seldom-used code, possibly indefinitely (if the code is never used). Furthermore, it opens up the opportunities for plugins and other extensions.