Get immediate value from UIALertView - iphone

Question

I have what can be most accurately described as a Factory, which is generating some NSOperations. Before the NSOPerations are generated, I would like to check the current network status and, if the user is on a 3G/Mobile connection, warn them that they are about to do a data-heavy operation.
I attempted to do this with a UIAlertView, but the only way I can see to get the "response" from a UIAlertView is via the event-based delegate system. I was wondering if there was any way to have it act like the "confirm" dialogue in JavaScript, where it blocks the UI and I can get an immediate value from it once it is dismissed.
Is there any standard way to do this, or some example code I could be pointed towards that accomplishes something similar?

Answer 1

Blocking the main thread is considered bad practice on iOS, and thus there is no synchronous API for UIAlertView.
You should implement a delegate callback for the alert that enqueues the relevant NSOperation. It may be useful to subclass UIAlertView to store the relevant data you need to enqueue the NSOperation, or better yet store a block that captures the relevant variables and then just execute that when the user confirms the dialog.

Answer 2

You can implement something similar to that, using blocks. The execution will continue as in all other cases, but the flow of reading your code might more resemble what you want. Here is a helper class that I made for that purpose so that I can just go:
[YUYesNoListener yesNoWithTitle:#"My Title" message:#"My Message" yesBlock:^
{
NSLog(#"YES PRESSED!");
}
noBlock:^
{
NSLog(#"NO PRESSED!");
}];
...and here is the helper class:
typedef void(^EmptyBlockType)();
#interface YUYesNoListener : NSObject <UIAlertViewDelegate>
#property (nonatomic, retain) EmptyBlockType yesBlock;
#property (nonatomic, retain) EmptyBlockType noBlock;
+ (void) yesNoWithTitle:(NSString*)title message:(NSString*)message yesBlock:(EmptyBlockType)yesBlock noBlock:(EmptyBlockType)noBlock;
#end
#implementation YUYesNoListener
#synthesize yesBlock = _yesBlock;
#synthesize noBlock = _noBlock;
- (id) initWithYesBlock:(EmptyBlockType)yesBlock noBlock:(EmptyBlockType)noBlock
{
self = [super init];
if (self)
{
self.yesBlock = [[yesBlock copy] autorelease];
self.noBlock = [[noBlock copy] autorelease];
}
return self;
}
- (void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
if (buttonIndex == 0 && self.noBlock)
self.noBlock();
else if (buttonIndex == 1 && self.yesBlock)
self.yesBlock();
[_yesBlock release];
[_noBlock release];
[alertView release];
[self release];
}
- (void) alertViewCancel:(UIAlertView *)alertView
{
if (self.noBlock)
self.noBlock();
[_yesBlock release];
[_noBlock release];
[alertView release];
[self release];
}
+ (void) yesNoWithTitle:(NSString*)title message:(NSString*)message yesBlock:(EmptyBlockType)yesBlock noBlock:(EmptyBlockType)noBlock
{
YUYesNoListener* yesNoListener = [[YUYesNoListener alloc] initWithYesBlock:yesBlock noBlock:noBlock];
[[[UIAlertView alloc] initWithTitle:title message:message delegate:yesNoListener cancelButtonTitle:#"No" otherButtonTitles:#"Yes", nil] show];
}
#end

Answer 3

Using the code of Ricky Helgesson, I've built a Pod component to use this solution easily in any project that uses CocoaPods.
https://github.com/nmaletm/STAlertView
The code that you should use is:
[[STAlertView alloc] initWithTitle:#"Title of the alert"
message:#"Message you want to show"
cancelButtonTitle:#"No" otherButtonTitles:#"Yes"
cancelButtonBlock:^{
// Code todo when the user cancel
...
} otherButtonBlock:^{
// Code todo when the user accept
...
}];
And add at the Podfile:
pod "STAlertView"
There are more instructions at the github page.