I got annoyed that NSAlert doesn’t have any SIMPLE way to add a checkbox to it, so I wrote this custom subclass to add it in, enjoy:

NSAlertCheckbox.h:

#import <Cocoa/Cocoa.h>

// private methods @interface NSAlert (CheckboxAdditions)

• (void)prepare;
• (id)buildAlertStyle:(int)fp8 title:(id)fp12 formattedMsg:(id)fp16 first:(id)fp20 second:(id)fp24 third:(id)fp28 oldStyle:(BOOL)fp32;
• (id)buildAlertStyle:(int)fp8 title:(id)fp12 message:(id)fp16 first:(id)fp20 second:(id)fp24 third:(id)fp28 oldStyle:(BOOL)fp32 args:(char *)fp36; @end

@interface NSAlertCheckbox : NSAlert { NSButton *_checkbox; }

• (NSAlertCheckbox *)alertWithMessageText:(NSString *)message defaultButton:(NSString *)defaultButton alternateButton:(NSString *)alternateButton otherButton:(NSString *)otherButton informativeText:(NSString *)format;

• (BOOL)showsCheckbox;

• (void)setShowsCheckbox:(BOOL)showsCheckbox;

• (NSString *)checkboxText;

• (void)setCheckboxText:(NSString *)text;

• (int)checkboxState;
• (void)setCheckboxState:(int)state; @end

NSAlertCheckbox.m:

#import “NSAlertCheckbox.h”

@interface NSAlertCheckbox (Private)

• (void)_addCheckboxToWindow; @end

@implementation NSAlertCheckbox

• (id)init { if (self = [super init]) { _checkbox = nil; }

  return self; }

• (void)dealloc { [_checkbox release];

  [super dealloc]; }

• (NSAlertCheckbox *)alertWithMessageText:(NSString *)message defaultButton:(NSString *)defaultButton alternateButton:(NSString *)alternateButton otherButton:(NSString *)otherButton informativeText:(NSString *)format { NSAlert *alert = [super alertWithMessageText:message defaultButton:defaultButton alternateButton:alternateButton otherButton:otherButton informativeTextWithFormat:format];

  return (NSAlertCheckbox *)alert; }

#pragma mark -

• (BOOL)showsCheckbox { return (_checkbox != nil); }

• (void)setShowsCheckbox:(BOOL)showsCheckbox { if (showsCheckbox && !_checkbox) { _checkbox = [[NSButton alloc] initWithFrame:NSZeroRect]; [_checkbox setButtonType:NSSwitchButton]; } else if (!showsCheckbox && _checkbox) { if ([_checkbox superview]) { [_checkbox removeFromSuperview]; } [_checkbox release]; _checkbox = nil; } }

• (NSString *)checkboxText { NSString *text = nil;

  if ([self showsCheckbox]) { text = [_checkbox title]; }

  return text; }

• (void)setCheckboxText:(NSString *)text { if ([self showsCheckbox]) { [_checkbox setTitle:text]; } }

• (int)checkboxState { int state = -1;

  if ([self showsCheckbox]) { state = [_checkbox state]; }

  return state; }

• (void)setCheckboxState:(int)state { if ([self showsCheckbox]) { [_checkbox setState:state]; } }

#pragma mark -

• (id)buildAlertStyle:(int)fp8 title:(id)fp12 formattedMsg:(id)fp16 first:(id)fp20 second:(id)fp24 third:(id)fp28 oldStyle:(BOOL)fp32 { id retVal = [super buildAlertStyle:fp8 title:fp12 formattedMsg:fp16 first:fp20 second:fp24 third:fp28 oldStyle:fp32]; [self _addCheckboxToWindow];

  return retVal; }

• (id)buildAlertStyle:(int)fp8 title:(id)fp12 message:(id)fp16 first:(id)fp20 second:(id)fp24 third:(id)fp28 oldStyle:(BOOL)fp32 args:(char *)fp36 { id retVal = [super buildAlertStyle:fp8 title:fp12 message:fp16 first:fp20 second:fp24 third:fp28 oldStyle:fp32 args:fp36]; [self _addCheckboxToWindow];

  return retVal; } @end

@implementation NSAlertCheckbox (Private)

• (void)_addCheckboxToWindow { float checkboxPadding = 14.0f; // according to the apple HIG

  if ([self showsCheckbox]) { NSWindow *window = [self window]; NSView *content = [window contentView];

    // find the position of the main text field
    NSArray *subviews = [content subviews];
    NSEnumerator *en = [subviews objectEnumerator];
    NSView *subview = nil;
    NSTextField *messageText = nil;
    int count = 0;
  	
    while (subview = [en nextObject]) {
        if ([subview isKindOfClass:[NSTextField class]]) {
            count++;
  			
            if (count == 2) {
                messageText = (NSTextField *)subview;
            }
        }
    }
  	
    if (messageText) {
        [content addSubview:_checkbox];
  		
        // make the checkbox font match the text area above it
        [_checkbox setFont:[messageText font]];
        [_checkbox sizeToFit];
  		
        // expand the window
        NSRect windowFrame = [window frame];
        NSRect checkboxFrame = [_checkbox frame];
        windowFrame.size.height += checkboxFrame.size.height + checkboxPadding;
        [window setFrame:windowFrame display:YES];
  		
        checkboxFrame.origin.y = [messageText frame].origin.y - checkboxFrame.size.height - checkboxPadding;
        checkboxFrame.origin.x = [messageText frame].origin.x;
  		
        [_checkbox setFrame:checkboxFrame];
        [window makeFirstResponder:self buttons] objectAtIndex:0;
    }   } } @end
  

Here’s some example code using it:

// prompt the user NSAlertCheckbox *alert = [NSAlertCheckbox alertWithMessageText:@”Install Flash” defaultButton:@”Download” alternateButton:@”No Thanks” otherButton:nil informativeText:@”The current verson of flash is out of date, do you wish to download the latest?”];

[alert setShowsCheckbox:YES]; [alert setCheckboxText:@”Don’t ask me again.”]; [alert setCheckboxState:NSOnState];

if ([alert runModal] == NSAlertDefaultReturn) { // go download flash }

if ([alert checkboxState] == NSOnState) { // go set a pref somewhere }

– TristanOTierney

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I’ve got some similar code that will use the private checkbox methods built into NSAlert, if they’re available, or fallback to a regular checkbox if the code appears to be missing. The advantage to this code is that there is less direct manipulation of the alert’s window and controls–i.e. it’s a higher-level implementation. If people would like, I can clean it up and post it as a download. - JonathanGrynspan

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TristanOTierney thanks and JonathanGrynspan, please do.

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Looks like Leopard allows you not only to set an accessory view to the NSAlert but to set a “suppression checkbox”. - DanGrover