UsingBlocksAsContextInfo/UsingBlocksAsContextInfoAppDelegate.m

/*
     File: UsingBlocksAsContextInfoAppDelegate.m 
 Abstract: The sample's application delegate used to manage its primary window and for showing how to use the NSAlert. 
  Version: 1.1 
  
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 */
 
#import "UsingBlocksAsContextInfoAppDelegate.h"
 
@implementation UsingBlocksAsContextInfoAppDelegate
 
// This is a quick tip on how to use the context info as a block parameter.
// You can use this type of pattern for any methods that have a delegate/selector/contextInfo pattern.
//
- (IBAction)btnShowAlertClicked:(id)sender {
    
    NSAlert *alert = [NSAlert alertWithMessageText:@"Alert Message"
                                     defaultButton:@"Default Button"
                                   alternateButton:@"Alternate Button"
                                       otherButton:@"Other Button"
                         informativeTextWithFormat:@"Informative Text"];
    
    BOOL someLocalVariable = YES;
    
    // We create a block that can easily access local variables to this method.
    // This is much easier than trying to package them all up into a contextInfo object
    void (^blockCallback)(NSInteger) = ^(NSInteger returnCode) {
        // Inside the block callback we can easily access locals
        if (someLocalVariable) {
            if (returnCode == NSAlertDefaultReturn) {
                [self.button setTitle:@"Default Return Button Clicked!"];
            } else {
                [self.button setTitle:@"Something else clicked...try again."];
            }
        }
    };
    
    // We copy the block, since it needs to stay alive for longer than the current scope
    [alert beginSheetModalForWindow:self.window
                      modalDelegate:[self class]
                     didEndSelector:@selector(alertDidEnd:returnCode:contextInfo:)
                        contextInfo:(void *)CFBridgingRetain([blockCallback copy])];
}
 
+ (void)alertDidEnd:(NSAlert *)alert returnCode:(NSInteger)returnCode contextInfo:(void (^)(NSInteger returnCode))continuationHandler {
    
    continuationHandler(returnCode);
    // The block must always be retained before the first call. This is the matching release
}
 
- (BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication *)sender {
    
    return YES;
}
 
@end