Since ALAssetsGroup or not valid after the life of ALAssetsLibrary
I'm saving ALAssetsGroupPropertyURL from valueForProperty
but this property is only available from iOS 5.0
How does one can get a hold of it in iOS 4.0+ ?
I went the ALAssetsGroupPropertyPersistentID way ...
since groupForURL:resultBlock:failureBlock: is for iOS 5.0+ anyways
Related
I have a question regarding iOS 4 and 5. I am really confused and hope someone will clear it out for me.
I am using iOS 5 SDK in my application. If i use the iOS 5 Twitter integration which is provided by apple, will it run on an iPhone that has iOS 4 installed ?
Does backward compatibility work ?
I have used Twitter as an example, but does backward compatibility really work with iOS 5 ?
If you set up your app properly, so that it can be run on devices running iOS 4 without crashing, then: yes, it will run on an iPhone that has iOS 4 installed.
Your app should implement logic such that the Twitter API is used when the app is being run on an iOS 5 device. When the app is running on an iOS 4 device, you can conditionally choose not to use the Twitter API.
Instead, you can use a different Twitter library (like MGTwitterEngine, or your own) - or just exclude Twitter functionality for those users.
To check whether the TWRequest Class exists, use NSClassFromString.
Class twRequestClass = NSClassFromString(#"TWRequest");
if (twRequestClass == nil) {
// TWRequest does not exist on this device (running iOS version < 5.0)
// ... do something appropriate ...
} else {
TWRequest *twRequest = [[twRequestClass alloc] init];
// ^ I didn't look up the proper initializer, so you should change that line if necessary
// ...
}
You would have to create ifs dependently of the iOS version the user is using. Exemple, in iOS 5 there is an Appearance API to modify most of the UI, but not in iOS 4, so you have to create a little if like that:
// not supported on iOS4
UINavigationBar *navBar = [myNavController navigationBar];
if ([navBar respondsToSelector:#selector(setBackgroundImage:forBarMetrics:)])
{
[navBar setBackgroundImage:[UIImage imageNamed:#"bg.jpg"] forBarMetrics:UIBarMetricsDefault];
}
If you set up your app properly, so that it can be run on devices running iOS 4, it will crash. This is because you're trying to access methods/features that arn't available.
The way to get around this is to check if a feature is available using
if(NSClassFromString(#"UIPopoverController")) {
// Do something
}
(Popover controller is just an example)
You could also check the version using
float version = [[[UIDevice currentDevice] systemVersion] floatValue];
And then depending on the version run a specific piece of code (i.e. if iOS 5, preform twitter stuff,else do something different)
No, if you use the Twitter APIs available in iOS5, they will not be able to run on iOS4.
The reason being that when app will run on iOS4, the system will not be having the APIs availability.
if you check the documentation, you can see the iOS version from where this Class/API is available.
I hope this helps..
My application was launched on the App Store on Oct. 5. It is working well on all iOS versions except iOS 5. On a particular class it is crashing on this statement:
[[self.tableView cellForRowAtIndexPath:lastIndex]
setAccessoryType:UITableViewCellAccessoryNone];
I am getting the error "Executing Bad Access."
Could this be because of ARC, introduced by Apple in iOS 5?
That indexPath should be retained.
Add [lastIndex retain]; before your statement.
i'm trying to add printing features to an ios app.
while printing itself works fine, and the app works on ios > 4, i haven't figured out yet how to keep the ios 3.1 compatibility...
i guess the issue is this: completionHandler:(UIPrintInteractionCompletionHandler)
A block of type UIPrintInteractionCompletionHandler that you implement to handle the
conclusion of the print job (for instance, to reset state) and to
handle any errors encountered in printing.
once i add the block:
void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {
};
the app won't even launch on iOS 3.1
probably because blocks aren't available there.
yes, i made sure that this code won't be run when launched on iOS 3.1...
if (([[[UIDevice currentDevice] systemVersion] floatValue] >= 4.2) && ([UIPrintInteractionController isPrintingAvailable]))
so i wonder if there's a way to have printing support for iOS >4.2, but keeping it to run on iOS 3.1?
maybe there's a way to use a method instead of the "block"?
or how would be the correct way to have printing available on supported iOS devices, and remain backwards compatible to iOS 3.1?
just add -weak_framework UIKit to the project settings under "Other Linker Flags" and make sure you use conditional code for printing API.
Conditional code should check feature availability, not OS version:
if (NSClassFromString(#"UIPrintInteractionController")){
void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {
};
}
Set your project target to iOS 3, and you're good to go.
The best practice for detecting if AirPrint is available is to use NSClassFromString. If you use this method in general, then you always know if exactly the class you want is available, without having to hard-code which features correspond with which version. Example code:
Class printControllerClass = NSClassFromString(#"UIPrintInteractionController");
if (printControllerClass) {
[self setupCanPrintUI];
} else {
[self setupCannotPrintUI];
}
That way your app can still work on previous iOS versions, although it won't be able to print from them.
I've been able to use this technique and run it on an iOS 3.0 device without any problems with the block code (the ^-based stuff). In my build settings, I have the Base SDK set to iOS 4.2, and the Deployment Target set to iOS 3.0.
I posted a sample Xcode project at the end of this blog post on printing in iOS. This is the project that successfully runs for me on a device with iOS 3.0 and another device with iOS 4.2. You may have to change the bundle identifier in the info.plist to get the code-signing to work for you, but that's independent of the printing stuff.
Set Deployment Target in your Project Settings to iOS 3.x. However, set the Base SDK to 4.2. Now you can use the 4.2 classes and iPhones running 3.x can install your app too.
Keep in mind that when you use a 4.2 class on an iPhone 3.x, the application will crash (so keep checking the system version on-the-go).
NSComparisonResult order = [[UIDevice currentDevice].systemVersion compare:#"3.2" options: NSNumericSearch];
if (order == NSOrderedSame || order == NSOrderedDescending && [[UIDevice currentDevice]isMultitaskingSupported]) {
// >4.2
}
else {
//< 4.2
}
Note:
also change UIKit framework setting from "required" to "weak" this will help you to run application on iOs < 4.2 as well as iOs >= 4.2
I made iPhone app with eventkit framework. However, i upgrade to universal app, app can't run in ipad. I got error message
dyld: Library not loaded: /System/Library/Frameworks/EventKit.framework/EventKit
Yes, event kit only work for iOS 4.0 or later. So, how to make it for universal.
I want to make , if iPad app, don't use event kit framework.
However, I can't add
#import <EventKit/EventKit.h>
#import <EventKitUI/EventKitUI.h>
in run time
You need to do two things:
First, weak link against the EventKit framework. You do this in Target->Get Info->General.
Secondly, you need to decide at run time whether or not certain functionality is available:
Class someClass = NSClassFromString(#"SomeClass");
if(someClass) {
// iOS4 code
}
else {
// iOS3.2 code
}
Need to make weak linking.
Right Click on Target -> Get Info -> General Tab
change Eventkit Framework required to weak.
I know this is a really weak answer, but the only answer if you need EventKit on the iPad: Wait until next month when iOS 4.2 ships for the iPad. At this time use the 4.2 beta to develop your universal app. Maybe your app can be ready when the App Store starts accepting apps requiring iOS 4.2.
I have a code for UIImage picker
photoImagePicker=[[UIImagePickerController alloc]init];
photoImagePicker.delegate=self;
photoImagePicker.sourceType=UIImagePickerControllerSourceTypeCamera;
photoImagePicker.mediaTypes=[UIImagePickerController availableMediaTypesForSourceType:photoImagePicker.sourceType];
[self presentModalViewController:photoImagePicker animated:YES];
photoImagePicker.showsCameraControls = YES; //Doesnot work on 3.0
photoImagePicker.navigationBarHidden = YES;
photoImagePicker.toolbarHidden = YES;
photoImagePicker.allowsEditing=YES; //Doesnt work on 3.0
Now everything works fine when the sdk is 3.1 or higher but when i put the os version as 3.0, the code starts showing errors. Turns out these methods were not present in 3.0 and so errors. I want to keep a mechanism which will enable these for higher versions(3.1) and at the same time work properly for 3.0 version.
How do i do it?
One solution i have thought of is to verify the version value and then put that code. But i am not sure how this is got. Any help will be appreciated.
I think you should be able to do it using Weak Linking. This article How to build a single iPhone application support both 2.x and 3.0 at the same time should also help.