5 ms·

A taste of CoreData – A graph framework

76 points by yageek 9y ago

_sdegutis 9y ago
Kudos to OP for braving through CoreData. I’ve been using it on and off since it was released, and it’s an awfully cumbersome and error-prone framework. And as Apple adds more complexity to iOS, CoreData gets exponentially worse. I’m 200% convinced today that it’s far better to just store your users data in a more traditional cloud database instead. Especially with syncing, which Apple made ridiculously, unnecessarily hard to get right.
- yageek 9y ago
  CoreData does not imply storing data on server. You can use it simply to model your data without persistency. The fact that CoreData is hard is that is not really well documented I would say.
- oligopoly 9y ago
  >I’m 200% convinced today that it’s far better to just store your users data in a more traditional cloud database instead What would you recommend? Firebase, Realm or something else for small project that might or might not get off the ground? Personally I've found the hardest thing tapping in iOS development there doesnt seem to be culture of writing out tutorials / problems people had and how they fixed them. Doing webdev you find countless similar issues people had and how they fixed them with simple google search. Lot of docs are in objective-c as well which kinda pushes you to study two languages instead of one. I tried React Native for a while but it's ridicules how fast stuff get deprecated and the feel is far from 'Native'.
  - kitsunesoba 9y ago
    What specifically are you having trouble finding tutorials for? I’ve had little issue finding ios tutorials for most things. This particular bit is far better than it used to be, back when Apple platform development meant Mac apps written in Obj-C and AppKit. Back then, your best hope were a handful of blog posts and mailing list threads. If your issue wasn’t there, you had to figure it out on your own. Today there are tutorials for Swift and UIKit springing up all over the place. It’s quite a change.
- hungerstrike 9y ago
  Yes, I’d rather just use SQLite. It works everywhere and it’s very easy to sync with a server.
- rimliu 9y ago
  I'd say CoreData got better, not exponentially worse. Also, too many think about it as database, which it explicitly is not.
mpweiher 9y ago
Since about 20003, I have made a bit of a career of removing CoreData and its predecessor EOF from applications. Every time it has been a huge success in terms of simplicity, performance and reliability. Replacing EOF happened in a feed-processing application[1]. We just processed everything in memory and persisted the incoming feed, which we wanted to do anyway for auditing. In that instance it wasn't so much a planned removal, but rather that we never came around to implementing the DB component. Next up was a desktop application, Livescribe Desktop. It was using an atomic store, so there wasn't really any point to CoreData. Chucking it meant removing a lot of code and crash-sites. For Wunderlist 3, we rewrote the storage layer to simply use a bunch of JSON files (our CTO used to shock people at conferences with that little nugget), and the "In-Process REST" ideas from [1]. So our persistence solution was essential [NSJSONSerialization dataWith...]. The day after we launched, I was shocked at the number of crash reports, but my colleagues informed me that they had 10x the amount the last time. With millions of users, you get into a lot of edge cases. Oh, ours was also the fastest of the clients. Oh, I also gave a talk at UIKonf '17 about making a public transport data (sample) application 1000x faster by moving from CoreData/sqlite to a custom data representation.[2] [1] https://link.springer.com/chapter/10.1007/978-1-4614-9299-3_11 https://link.springer.com/chapter/10.1007/978-1-4614-9299-3_... [2] https://www.youtube.com/watch?v=kHG_zw75SjE&feature=youtu.be https://www.youtube.com/watch?v=kHG_zw75SjE&feature=youtu.be
- yageek 9y ago
  The purpose of the post is just to provide some general information about the different concepts provided by CoreData. The framework first lacks of a clear documentation I would say. Regarding reliability, if the rules are respected, I would consider CoreData as a reliable framework. Regarding speed, I would say that CoreData is far lower than other low level approach. It is up to the developer to estimate the needs in term of speed/performance. The biggest advantage of CoreData, according to me, would be the integration with the UI libraries, but this is only my opinion :) I guess you gave the same talk at appbuilders last year right?
RantyDave 9y ago
NSPredicate. Back in the day I fought through the CoreData only kinda SQL thing and eventually got a result but... These days I'd just shove it on SQLite and get 10x the performance for 10x less effort. God DAMN that was hard work. https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Predicates/AdditionalChapters/Introduction.html#//apple_ref/doc/uid/TP40001789 https://developer.apple.com/library/content/documentation/Co...
- danieleggert 9y ago
  Well, that’s a common misconception, but far from the truth. If you actually care about performance, you’ll soon find out that performance wrt. database work is all about high-level optimizations: You want to reduce the times you hit the database (both reads and particularly writes). And once you’re getting into that busyness, Core Data will allow you to create way faster coder in less time. Core Data will get you 10x the performance for 10x less effort.
  - mpweiher 9y ago
    Hmm...parent is actually correct. What you write is true with very slow databases, particularly when talking to enterprise databases over a network. "Fortunately", CoreData is so slow that as long as you stay within that universe, your view will never be invalidated. Outside, however, computers are blazingly fast in general and I/O throughput is also incredibly fast. My laptop can read/write 2 GB/s. That's a lot. Moby Dick is around 1.25 MB. This means that you can write this whale of a book, in its entirety, 800 times per second. That's a lot. But I repeat myself...because it's worth repeating. CoreData helps you optimize/minimize the size of transactions. Except for a very few cases, that's the wrong thing to optimize, as all our storage has amazing throughput and not-so good per-transaction and seek costs. Getting 1 byte from disk is almost as expensive as getting 1 megabyte, and having a bunch of smaller transactions is almost always a loss compared to one large transaction.
Unknoob 9y ago
I've been using CoreData in a big project but the multithreading has been crashing my app a lot. Can anyone recommend me some alternatives for a simple, lightweight, 100% local data storage for iOS?
- vlozko 9y ago
  I've always felt that mastering CoreData's multi-threaded APIs are a trial by fire. Tutorials and recommendations only got me so far and I had to stumble my way through to truly master it. At the end of it all, I got a bigger feeling of appreciation for the complexities involved in multi-threaded synching of data and its persistence.
- jinjin2 9y ago
  Realm (https://Realm.io https://Realm.io) is an amazing alternative to CoreData.
- yageek 9y ago
  I woudl say you can not have a threadsafe persistence framework. In all the case, you will need to handle the concurrency manually. Can you provide more precise details about how you encountered the crashes?

76 points by yageek 9y ago

Kudos to OP for braving through CoreData. I’ve been using it on and off since it was released, and it’s an awfully cumbersome and error-prone framework. And as Apple adds more complexity to iOS, CoreData gets exponentially worse. I’m 200% convinced today that it’s far better to just store your users data in a more traditional cloud database instead. Especially with syncing, which Apple made ridiculously, unnecessarily hard to get right.

yageek 9y ago
CoreData does not imply storing data on server. You can use it simply to model your data without persistency. The fact that CoreData is hard is that is not really well documented I would say.
oligopoly 9y ago
>I’m 200% convinced today that it’s far better to just store your users data in a more traditional cloud database instead What would you recommend? Firebase, Realm or something else for small project that might or might not get off the ground? Personally I've found the hardest thing tapping in iOS development there doesnt seem to be culture of writing out tutorials / problems people had and how they fixed them. Doing webdev you find countless similar issues people had and how they fixed them with simple google search. Lot of docs are in objective-c as well which kinda pushes you to study two languages instead of one. I tried React Native for a while but it's ridicules how fast stuff get deprecated and the feel is far from 'Native'.
- kitsunesoba 9y ago
  What specifically are you having trouble finding tutorials for? I’ve had little issue finding ios tutorials for most things. This particular bit is far better than it used to be, back when Apple platform development meant Mac apps written in Obj-C and AppKit. Back then, your best hope were a handful of blog posts and mailing list threads. If your issue wasn’t there, you had to figure it out on your own. Today there are tutorials for Swift and UIKit springing up all over the place. It’s quite a change.
hungerstrike 9y ago
Yes, I’d rather just use SQLite. It works everywhere and it’s very easy to sync with a server.
rimliu 9y ago
I'd say CoreData got better, not exponentially worse. Also, too many think about it as database, which it explicitly is not.

mpweiher 9y ago

Since about 20003, I have made a bit of a career of removing CoreData and its predecessor EOF from applications. Every time it has been a huge success in terms of simplicity, performance and reliability. Replacing EOF happened in a feed-processing application[1]. We just processed everything in memory and persisted the incoming feed, which we wanted to do anyway for auditing. In that instance it wasn't so much a planned removal, but rather that we never came around to implementing the DB component. Next up was a desktop application, Livescribe Desktop. It was using an atomic store, so there wasn't really any point to CoreData. Chucking it meant removing a lot of code and crash-sites. For Wunderlist 3, we rewrote the storage layer to simply use a bunch of JSON files (our CTO used to shock people at conferences with that little nugget), and the "In-Process REST" ideas from [1]. So our persistence solution was essential [NSJSONSerialization dataWith...]. The day after we launched, I was shocked at the number of crash reports, but my colleagues informed me that they had 10x the amount the last time. With millions of users, you get into a lot of edge cases. Oh, ours was also the fastest of the clients. Oh, I also gave a talk at UIKonf '17 about making a public transport data (sample) application 1000x faster by moving from CoreData/sqlite to a custom data representation.[2] [1] https://link.springer.com/chapter/10.1007/978-1-4614-9299-3_11 https://link.springer.com/chapter/10.1007/978-1-4614-9299-3_... [2] https://www.youtube.com/watch?v=kHG_zw75SjE&feature=youtu.be https://www.youtube.com/watch?v=kHG_zw75SjE&feature=youtu.be

yageek 9y ago
The purpose of the post is just to provide some general information about the different concepts provided by CoreData. The framework first lacks of a clear documentation I would say. Regarding reliability, if the rules are respected, I would consider CoreData as a reliable framework. Regarding speed, I would say that CoreData is far lower than other low level approach. It is up to the developer to estimate the needs in term of speed/performance. The biggest advantage of CoreData, according to me, would be the integration with the UI libraries, but this is only my opinion :) I guess you gave the same talk at appbuilders last year right?

RantyDave 9y ago

NSPredicate. Back in the day I fought through the CoreData only kinda SQL thing and eventually got a result but... These days I'd just shove it on SQLite and get 10x the performance for 10x less effort. God DAMN that was hard work. https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Predicates/AdditionalChapters/Introduction.html#//apple_ref/doc/uid/TP40001789 https://developer.apple.com/library/content/documentation/Co...

danieleggert 9y ago
Well, that’s a common misconception, but far from the truth. If you actually care about performance, you’ll soon find out that performance wrt. database work is all about high-level optimizations: You want to reduce the times you hit the database (both reads and particularly writes). And once you’re getting into that busyness, Core Data will allow you to create way faster coder in less time. Core Data will get you 10x the performance for 10x less effort.
- mpweiher 9y ago
  Hmm...parent is actually correct. What you write is true with very slow databases, particularly when talking to enterprise databases over a network. "Fortunately", CoreData is so slow that as long as you stay within that universe, your view will never be invalidated. Outside, however, computers are blazingly fast in general and I/O throughput is also incredibly fast. My laptop can read/write 2 GB/s. That's a lot. Moby Dick is around 1.25 MB. This means that you can write this whale of a book, in its entirety, 800 times per second. That's a lot. But I repeat myself...because it's worth repeating. CoreData helps you optimize/minimize the size of transactions. Except for a very few cases, that's the wrong thing to optimize, as all our storage has amazing throughput and not-so good per-transaction and seek costs. Getting 1 byte from disk is almost as expensive as getting 1 megabyte, and having a bunch of smaller transactions is almost always a loss compared to one large transaction.

Unknoob 9y ago

I've been using CoreData in a big project but the multithreading has been crashing my app a lot. Can anyone recommend me some alternatives for a simple, lightweight, 100% local data storage for iOS?

vlozko 9y ago
I've always felt that mastering CoreData's multi-threaded APIs are a trial by fire. Tutorials and recommendations only got me so far and I had to stumble my way through to truly master it. At the end of it all, I got a bigger feeling of appreciation for the complexities involved in multi-threaded synching of data and its persistence.
jinjin2 9y ago
Realm (https://Realm.io https://Realm.io) is an amazing alternative to CoreData.
yageek 9y ago
I woudl say you can not have a threadsafe persistence framework. In all the case, you will need to handle the concurrency manually. Can you provide more precise details about how you encountered the crashes?