Airbnb is 75% executables, 9.5% assets and 8% localizations. This is pretty different from Uber which is 60.7% executables, 26% localizations and only 3.8% assets. While the Uber executables are large, ~10mb more than Airbnb (note: this is only the Uber rider app, while Airbnb has host+guest in one app), their localizations seem to be driving a lot of the app’s 300+mb install size.
Looking at how the localizations are laid out in the app bundle, there are thousands of *.strings files in separate bundles, seems to be one for each feature. Many of these files have comments to provide context for the strings. An example from the app is: "Various screens show this as a title in a snackbar message when there is no network connectivity available". Just stripping these comments out of the localization files would save about 17.6mb of the install size. Another side effect of splitting localizations into so many files is there are over 23k duplicated strings throughout these bundles.
While the Swift code size is part of the problem with Uber’s app size, it's not the only way to free up space. There's a lot of work that goes into bringing a large scale iOS app’s size down, and not many tools to help. I left my job at Airbnb recently to work on making it easier to visualize, monitor and reduce app size, please email me (noah [at] emergetools.com) if you might be interested!
Lately Apple has been featuring size more prominently on the App Store, and it appears to be displaying the install size. This is also what users see when they look at which apps are taking up storage on their device in Settings. I think it’s important to reduce both, so users see a good number and downloads are fast/efficient. It is a very welcome change that binary encryption doesn’t negate all the gains from compression anymore. I had noticed it in the numbers but looked around for an official statement and didn’t find any, if you happen to know where this was announced I’d appreciate a link!
The Amsterdam team 100% played a critical role in solving the issue (at least until apple bumped the limit). No way we would have stayed under it without you all.
The OP indicates that a rewrite was necessary regardless. Even if Swift was not yet mature, do you think it was more worthwhile than rewriting in ObjC? Given that the goal was to "sustain mobile development at Uber for the next 5 years".
Secondly, I'm not a mobile developer so I don't have much context, and I'm wondering about your outlook on iOS development as a whole. Swift obviously had major problems but has supposedly gotten much better. You mention MacStadium's issues, but Apple build servers seem to be making progress with the recent AWS EC2 Mac reveal.
Is the iOS landscape turning a corner, or do you expect a new generation of bad developer experience?
I love Swift. But I've been adopting it in bits and pieces over the years. It's not just that the language has changed significantly, you also have to get used to the idioms. E.g. my early Swift code often featured Pyramid of Doom patterns, and both language innovations and better familiarity with the idioms have helped a lot with this.
Apple should have never pushed Swift as hard as it did at the time. Between the constant API changes and issues like requiring dynamic framework linkage and copying the whole runtime into every app, it was absolutely not production ready.
We didn't do a simple build scalability test until we were well into the project. If we did it would of revealed swift's build problems to us. Our swift experience is what slowed down our kotlin migration significantly. Today Uber android is still a majority Java app.
Even very recently the experience of working in swift compared to the old obj-c code base isn't as good. To this day there are debugger issues, xcode responsiveness issues and a slower build time.
Hiring on the other hand would be harder now, because it's getting hard to find people who know Objective-C and it's surface ugliness scares new people away. Swift is a decent language if you don't have to have a very large code base, so most people rightfully so don't have that much Objective-C, and if you were to work in Obj-C, you might as well go work at Facebook then.
I havent dabbled in mobile developer platform tooling for the last few years now so I cannot comment on the iOS side, all i remember is that back then it was a shitshow :) Mobile is still playing catch up to how backend infra and tooling operates, I suspect its better but probably still got a long way to go.
I hate objective C with a passion. It's like some archaic language of a bygone era forced to run on a cell phone
I personally find lower level programing to be frustrating and difficult. I've built an amazing career with JavaScript and C# primarily. My hobbyist projects use C# , JS and Flutter.
I can't wrap my head around things like pointers or memory management
With swift & obj-c your coding against the same library APIs, so in many ways it's a very similar level of programming. In many ways swift is far more complicated than Obj-C. With Obj-C iOS apps your not really writing that much C vs. the pseudo-smalltalk attachment to it.
Problem here with Swift came down to
- Apple not dogfooding its own tech . Hell they did not even help us or other major companies like AirBnB and LihnkedIn (We formed a workforce on this problem with them which then forced the download limit to be upped by apple)
- Engineers deciding to adopt a language which they thought was great (and turned out not to be at the time) because they did not do the right analysis upfront for such a significant project. 'Wow look at this shiny new cool tool, lets use it' (Oversimpiification, swift was more pleasant to write with and you could be more productive which was no doubt a factor here)
Also, while management at the time didnt care for the remote offices much, I think the AMS team played a critical role in the success here. With the recent layoffs that occurred, I heard that they were fired.
Another fun story, we were trying to bring down our build times on our CI builds which were 1hr+ while battling macstadium and their crappy infrastructure with tens/hundreds of patches incoming each day.