Block for UIAlertViewDelegate - iphone

Question

I'm pretty new to objective C and I'm just trying to figure out if I can use a block or a selector as the UIAlertViewDelegate argument for UIAlertView - and which is more appropriate?
I've tried the following but it just isn't working so I'm not sure if I'm on the right track or not?
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Checked In"
message:responseString
delegate:^(UIAlertView * alertView, NSInteger buttonIndex)
{
NSLog(#"Done!");
}
cancelButtonTitle:#"OK"
otherButtonTitles: nil];
Thanks!

Answer 1

Great idea. Here it is. Just like alert view, except adds a block property that's invoked when the alert is dismissed. (Edit - I've simplified this code since the original answer. Here's what I use now in projects)
// AlertView.h
//
#import <UIKit/UIKit.h>
#interface AlertView : UIAlertView
#property (copy, nonatomic) void (^completion)(BOOL, NSInteger);
- (id)initWithTitle:(NSString *)title message:(NSString *)message cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSArray *)otherButtonTitles;
#end
//
// AlertView.m
#import "AlertView.h"
#interface AlertView () <UIAlertViewDelegate>
#end
#implementation AlertView
- (id)initWithTitle:(NSString *)title message:(NSString *)message cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSArray *)otherButtonTitles {
self = [self initWithTitle:title message:message delegate:self cancelButtonTitle:cancelButtonTitle otherButtonTitles:nil];
if (self) {
for (NSString *buttonTitle in otherButtonTitles) {
[self addButtonWithTitle:buttonTitle];
}
}
return self;
}
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
if (self.completion) {
self.completion(buttonIndex==self.cancelButtonIndex, buttonIndex);
self.completion = nil;
}
}
#end
You can extend this idea to supply blocks for other delegate methods, but the didDismiss is the most common.
Call it like this:
AlertView *alert = [[AlertView alloc] initWithTitle:#"Really Delete" message:#"Do you really want to delete everything?" cancelButtonTitle:#"Nevermind" otherButtonTitles:#[#"Yes"]];
alert.completion = ^(BOOL cancelled, NSInteger buttonIndex) {
if (!cancelled) {
[self deleteEverything];
}
};
[alert show];

Answer 2

One must use UIAlertController for that approach as Apple document says
A UIAlertController object displays an alert message to the user. This
class replaces the UIActionSheet and UIAlertView classes for
displaying alerts. After configuring the alert controller with the
actions and style you want, present it using the
presentViewController:animated:completion: method.
In addition to displaying a message to a user, you can associate
actions with your alert controller to give the user a way to respond.
For each action you add using the addAction: method, the alert
controller configures a button with the action details. When the user
taps that action, the alert controller executes the block you provided
when creating the action object.
Apple Docs.
UIAlertController* alert = [UIAlertController alertControllerWithTitle:#"My Alert"
message:#"This is an alert."
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:#"OK" style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {}];
[alert addAction:defaultAction];
[self presentViewController:alert animated:YES completion:nil];

Answer 3

Check out this UIAlertView-Blocks category on github. I use this and it works well.

Answer 4

This is an update to danh's implementation, which is incomplete because it is not possible to add multiple buttons. Passing a va_list to a function is a little tricky :-)
So you could do this, in order to be able to add multiple buttons to the UIAlertView:
- (id)initWithTitle:(NSString *)title message:(NSString *)message completion:(void (^)(NSInteger buttonIndex))completion cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, ... {
self = [super initWithTitle:title message:message delegate:self cancelButtonTitle:cancelButtonTitle otherButtonTitles:nil ];
if(self){
_completion = completion;
va_list _arguments;
va_start(_arguments, otherButtonTitles);
for (NSString *key = otherButtonTitles; key != nil; key = (__bridge NSString *)va_arg(_arguments, void *)) {
[self addButtonWithTitle:key];
}
va_end(_arguments);
}
return self;
}
Update: There might be a better way of passing the va_list to super. I would like to mention that to me va_lists have something mystic to them :-)

Answer 5

Awesome idea. I have just completed exactly your idea using Category pattern, no subclass, call directly UIAlertView. Please follow these steps:
Category UIAlertView in .h file
#interface UIAlertView (AlertWithBlock)
- (void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegateBlock;
- (void)setDelegateBlock:(void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegateBlock;
+ (id)alertWithTitle:(NSString *)title message:(NSString *)message cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSArray *)otherButtonTitles delegate:(void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegate;
#end
In .m file
#implementation UIAlertView(AlertWithBlock)
static char const *delegateBlockTagKey = "delegateBlockTagKey";
- (void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegateBlock
{
return objc_getAssociatedObject(self, delegateBlockTagKey);
}
- (void)setDelegateBlock:(void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegateBlock
{
objc_setAssociatedObject(self, delegateBlockTagKey, delegateBlock, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
+ (id)alertWithTitle:(NSString *)title message:(NSString *)message cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSArray *)otherButtonTitles delegate:(void (^)(UIAlertView *alertView, NSInteger buttonIndex))delegate
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:message delegate:nil cancelButtonTitle:cancelButtonTitle otherButtonTitles:nil];
alert.delegate = alert;
alert.delegateBlock = [delegate copy];
for (NSString *buttonTitle in otherButtonTitles)
{
[alert addButtonWithTitle:buttonTitle];
}
[alert show];
return alert;
}
#pragma mark - Delegate
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
if (alertView.delegateBlock)
{
alertView.delegateBlock(alertView, buttonIndex);
}
}
#end
Call like this
[UIAlertView alertWithTitle:#"Title" message:#"This is a message" cancelButtonTitle:#"Cancel" otherButtonTitles:#[#"Yes",#"No"] delegate:^(UIAlertView *alertView, NSInteger buttonIndex) {
NSLog(#"Click at button index %ld", buttonIndex);
}];
Hope it help.

Answer 6

I have written a simple extension in Swift, hope it helpful
import UIKit
extension UIAlertView {
func show(completion: (alertView: UIAlertView, buttonIndex: Int) -> Void){
self.delegate = AlertViewDelegate(completion: completion)
self.show()
}
class func showInput(title: String?, message: String?, cancellable: Bool, completion: (text: String?) -> Void){
var strOK = NSLocalizedString("OK",comment: "OK")
var strCancel = NSLocalizedString("Cancel",comment: "Cancel")
var alert = UIAlertView(title: title, message: message, delegate: nil, cancelButtonTitle: cancellable ? strCancel : strOK)
alert.alertViewStyle = UIAlertViewStyle.PlainTextInput
if(cancellable) {
alert.addButtonWithTitle(strOK)
}
alert.show { (alertView, buttonIndex) -> Void in
if(cancellable && alertView.cancelButtonIndex == buttonIndex) {
completion(text: nil)
return
}
completion(text: alertView.textFieldAtIndex(0)?.text)
}
}
private class AlertViewDelegate : NSObject, UIAlertViewDelegate {
var completion : (alertView: UIAlertView, buttonIndex: Int) -> Void
var retainedSelf : NSObject?
init(completion: (UIAlertView, Int) -> Void ) {
self.completion = completion
super.init()
self.retainedSelf = self
}
func alertView(alertView: UIAlertView, didDismissWithButtonIndex buttonIndex: Int) {
var retain = self
retain.retainedSelf = nil
retain.completion(alertView: alertView, buttonIndex: buttonIndex)
}
}
}

Answer 7

Here is my implementation, seems like it's similar to most answers here:
http://stavash.wordpress.com/2013/01/31/quick-tip-uialertview-with-a-block-callback/

Answer 8

Simply use REKit. It's similar to BlocksKit, but it's more powerful.

Answer 9

Check out UIAlertView-Blocks category on Github.
I wrote this and is very easy to use and works well.
Good luck.

Answer 10

Here is another useful library to do the same. http://bit.ly/ichalrtvw
Code here: http://bit.ly/ichalertview

Answer 11

I had to edit the calling example a bit to stop complier error. Just a small tweak and xcode was happy.
UIAlertViewBlock *alert = [[UIAlertViewBlock alloc] initWithTitle:#"hi"
message:#"hi there"
completion:^(BOOL canceled,NSInteger buttonIndex) {
NSLog(#"canceled=%d", canceled);
NSLog(#"pressed=%d", buttonIndex);
}
cancelButtonTitle:#"cancel"
otherButtonTitles:#"ok", nil];
[alert show];