As Apple adds new APIs and new methods to APIs with every new iOS update or release and given that nowadays you can't even test on an iOS 3.x simulator, is there any way to test your iPhone app in older SDKs or to know what SDK level you are using through it?
Downgrading to an old Xcode with a 3.x simulator is not an option and, well, there are tons of methods introduced in, say, 4.2.
Has any one come up with a lib, script, tool, anything, that analyzes the code to show API usage?
The way most iOS developers do this is to keep around an old 1st or 2nd generation iPod Touch (or other old iPhone device) that hasn't been updated past the oldest iPhone OS version that they plan on supporting with their Deployment Target setting.
A cheap used iOS device, even with a scratched/cracked display or mostly dead battery, from eBay (et.al. or some neighbor or nephew who upgraded), might work.
Testing on an old device is actually a better and more accurate check than just testing with the Simulator, as the Simulator for various SDK versions supported APIs that the device at that OS level did not.
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Trying to keep up with the curve. I'm reading almost too much and is sending me in a tail spin. Is there a one stop link which will tell me what my target should be to run my app on all platforms based on what frameworks I have included? I make heavy use of Mapkit, and want to include iAds. My current apps seem dead on 3G.
Does Apple force you to support only the latest iOS? I have no problem with that, but not sure if someone who has and ancient 3G, how do I tell them, NO I don't support your phone, please upgrade?
Set your project's base SDK to the latest version of the SDK. Set the deployment target to the oldest version of the OS that you plan to support. You can use features introduced in versions later than your deployment target, but you'll need to check for them before you use them, else your app will crash.
Read the release notes for each version of the OS to get a good idea of what features were introduced when. In fact, make it a habit to read the release notes thoroughly each time a new version comes out.
iOS 4.2 runs pretty well on an iPhone 3G, so there's no need to drop support for the 3G anytime soon. If your apps currently don't work on the 3G, fire up your debugger and figure out why. What version of iOS are you running on that device? Where does it crash? This is typical debugging stuff.
Please how can I make sure before developing my iPhone app that it will be compatible with iPhone4, 3GS, iPod touch and 3G?
You need to create the app keeping in mind all the features available in lowest version of iPhone you need it to be compatible to.
For Example:
Suppose you want it to be compatible to iPhone 2G then you cannot use in-app SMS feature as iPhone 2G cannot be upgraded to iOS 4.0 or higher.
In-app SMS feature is only available in iOS 4.0 and higher versions.
Hope this example gave you a proper idea.
Once the app is made, you should test your app throughly on different devices i.e. iPhone 3G, iPhone 3GS and iPhone 4 and iPod Touch.
Unless you test it on device, you cannot be sure because sometimes some of the things work in simulator but crashes on device.
So better to test on device.
Hope this helps you.
If it's the SDK you are talking about, you might want to make sure it runs on iOS 3.X versions. See here for more details.
If it's the hardware you are talking about, you will need to test your app on separate pieces of hardware to make sure that they all run.
The settings in XCode that you make regarding which version of iOS your app will be compatible with is the iOS deployment target and the Base SDK. The Base SDK is the default version you are building against (this should be set to the most recent SDK which is currently 4.3). The iOS deployment target is the earliest version you would like your app to be available for (currently goes back to 3.0 on XCode 4).
These settings are in the settings for your target.
As for if your app will actually work on all of these devices depends on how you program for them. In other words, if you are using new APIs, they obviously will not work on versions that did not implement them.
Hope this helps.
Jamie
You can't be sure without testing. (and even with testing, some say...)
There are potential "gothcha's" in the iOS API documentation, in the Simulator handling of those APIs, and particularly in device performance, which you may not realize or be able to guess until you actually try an app out on all the device models and iOS versions which you plan to support.
Even some simple apps with no undocumented API use and no compiler or analyzer warnings, et.al., have been know to "break" after a new OS version is released.
You can "claim" an app is compatible by appropriate setting of the Deployment Target in the Build settings, lack of plist hardware restrictions, and in the app store submission data. But that's only a claim, not compatibility.
I have the following problem, in near future I will need to write a few not very complicated apps for iPhone. I do not currently own an iPhone, so I plan to purchase one for testing purposes. In short would iPhone 4 allow me to test apps written for older ios versions? Any pitfalls? Or would I have to purchase older phones/ipad to do the testing properly?
Yes, to perform a proper test you will need to test on the individual devices you are supporting. The documentation will tell you if the framework/API you are using is supported in the older iOS versions. I'm afraid there will be some subjective answers here as I am sure some apps end up running just fine across many versions with simulator testing. There are many factors to consider when looking at backwards compatibility (desired speed, memory usage, APIs, ...). You stated your app is "not very complicated" so you may be fine. I would test your application on as many devices as possible.
I should also make the distinction that there is a difference between "will it compile" and "does it perform as expected". You can use xcode to test whether the application is compatible by targeting and older version. Whether or not the application runs as desired will be discovered when testing on the specific devices.
You can't run iOS 3 on iPhone 4, so you have to buy separate devices.
But if it is a new app I wouldn't consider to make it iOS3 compatible. Most users have upgraded to iOS4 already. And at the time your app is in the store there will be even less users running iOS3.
Sure, this will remove like 0,5% of potential customers. But you don't want to buy another device for 100$ if you can get only 10$ revenue from the 0,5% customers that run iOS3. And you have to test your whole app again, which will take a significant amount of time.
So you should consider to drop support for iOS3.
See this question: Will an application compiled for iOS 3 run on iOS 4?
It will allow you to test apps which are targeted at older iOS versions, yes.
Performance differences to older iDevices like the 1st gen iPhone / iPod touch are quite significant however. So if your apps require expensive calculations or the like, I'd recommend buying an older, used device too to get a feeling for performance on that generation of hardware.
Note that if you need to make sure the apps you are about to develop will run on very old devices / iOS versions, you maybe need to do without some cocoa classes and methods which require more recent versions of iOS
If you bought an iPhone 4 for testing purpose.. You're testing on the latest iPhone available in the market and that doesn't means your app is ready to target low-end device automatically.
Let's take a deep look: If you've designed an App that must look gorgeous and work right out of the box on iPhone 4, then you're probably making your app a Retina display compatible. That is like playing with 960x640 resolution screen.
Now, if you planned to target low-end device for eg, iPhone 3GS, then all you gotta do is to reduce the graphic assets size by half, as iPhone 3GS is 320x480
That's it! Your App is ready for the low-end device as well, in looks and feels perspective.
Now, let's look from deployment perspective. If you base SDK is 4.2.1 and you're targeting to devices which runs 3.3, then all you gotta do is to make sure you don't use latest libraries/classes which are introduced in iOS 4.2.1, as they won't be available to device which are running on iOS 3.3. If you take care of this part, your app is almost ready to ship out.
From Market perspective. I see all the great apps out there had made their deployment target as iOS 4.0 or later. That means, they are targeting to only devices which runs iOS 4.0 or later versions.
I think, you can try your build in low-end iPhone simulator after successful testing cycles ran on iPhone 4 device. :)
The iPhone is generally not backwards compatible. Sometimes methods, properties, classes etc. are added or older ones become deprecated.
For testing, i would recommend that you have several devices with different iOS Versions depending on the target iOS Version you want to release.
Also check the the iOS Reference Library: Under "Availability" for each function etc. is noted since when it is Available
I am getting a fat binary when I go to upload, and I want to make sure that my application can run across 3.0, well even 2.0. Is there a specific way to make sure that this will show when I go to upload. I am not using any specific iOS 4 features, and I only have iOS 4 in my xCode. How can I test different iOS version?
The only way as I could think of is test your app on real old OS version devices. Since Apple prefers its users to upgrade to new OS version as soon as possible, they don't actually provide an official way for developers to test such backward compatibility.
Another relevant questions would be, "can I downgrade my device OS version to an old one, so that I can test my app on them?" I once did a research on SO and other Apple forums, and the result I got was NO, we developers don't have a way to "officially" downgrade our device OS version. Yes there are exceptions, you can try jail-breaking and then downgrading.
For jail-breaking / downgrading your OS version, check this post, A TimeMachine taking my iDevice back to 3.1.2? .
Edited: It's actually pretty easy to make sure that users with old OS versions can downloaded and install your app. All you need to do is set the Deployment Target in Xcode to the lowest OS version you want (iOS 3.0 would be the lowest in Xcode 3.2.5).
However, you need to bear in mind that such Deployment Target only ensures that your app can be downloaded and installed on such old version OS devices. They don't ensure compatibility during runtime. You still need to test your app on real old OS devices to ensure compatibility.
I dont think u need to worry about app version 3.0 below because it is not supported anymore. but how to test on different version, make sure change the iOS deployment target as Thomas refered.
There is no currently supported way to do this.
No current Simulator or Xcode tool will ensure that an app is completely compatible with an OS version older than the SDK used. The 2.0 SDK is not compatible with the current development tools. There is no officially supported way to downgrade a device.
Furthermore, Apple no longer even accepts app submissions that have a deployment target lower than 3.0.
Even most old 1st gen devices, if you can find one on eBay, have been upgraded to iOS 3.1.3. But if you have access to an old device running iOS 3.1.3, you can use that for testing. Many developers keep an old used iPod Touch around for just his purpose.
People with devices running something older than 3.1.3 are not only a really tiny percentage of the installed base, but are very unlikely to be still buying apps for that device. Even large developers with staff and legacy hardware available for this testing rarely waste the time on this market.
Look into Project -> Edit Project Settings -> iOS Deployment Target: 3.13. And then build?
Edit according to comment: You still need to ENSURE your code is within the runtime scope, i.e. do checks like 'respondstoselector' before calling methods in question.
i am new to iphone apps development.i want to develop Iphone applicaiton.which version i need to use and that should support run older and new version of Iphone.
which device is best for testing apps like 2g,3g,3gs
Thanks in advance
Aswan
It depends on the application. I am focused on games, so my target devices are 3G and iPod Touch (not the new one). Something older may be quite too restrictive for some ideas... At some point I will switch to the new 'retina display' models. But not now: the cake is still way too big with the not-so-old models!
Nevertheless, Apple forces you to use the latest XCode (4.1 devices). However, while you are forced to use the latest SDK, you may still target older devices (3.0 in our case, for example). You may go back to 2.1.1 devices, if I remember well.
Good luck!