Monitor NSTextFiled for a pause during user input.

NSTextField+controlTextDidPause.h

//
//  NSTextField+controlTextDidPause.h
//
//  Created by Eldon Ahrold on 5/23/15.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import <Cocoa/Cocoa.h>

@interface NSTextField (controlTextDidPause)
- (void)observeControlTextDidPause:(void (^)())paused;
- (void)stopObservingControlTextDidPause;
@end

NSTextField+controlTextDidPause.m

//
//  NSTextField+controlTextDidPause.m
//
//  Created by Eldon Ahrold on 5/23/15.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import "NSTextField+controlTextDidPause.h"
#import <objc/runtime.h>

@interface NSTextField (controlTextDidPausePrivate)
@property (copy) void (^controlTextPausedBlock)();
@end

@implementation NSTextField (controlTextDidPausePrivate)
@dynamic controlTextPausedBlock;

- (void)dealloc
{
    [self stopObservingControlTextDidPause];
}

- (void)stopObservingControlTextDidPause
{
    [[NSNotificationCenter defaultCenter]
        removeObserver:self
                  name:NSControlTextDidChangeNotification
                object:nil];
    self.controlTextPausedBlock = nil;
}

- (void)observeControlTextDidPause:(void (^)())didPause
{
    NSAssert([NSThread isMainThread],
             @"Observing control text must be executed on the main thread.");
    NSAssert(didPause, @"The reply block must not be nil");

    self.controlTextPausedBlock = didPause;

    [[NSNotificationCenter defaultCenter]
        addObserver:self
           selector:@selector(watchForPause)
               name:NSControlTextDidChangeNotification
             object:nil];
}

- (void)watchForPause
{
    [NSObject cancelPreviousPerformRequestsWithTarget:self
                                             selector:@selector(editingDidPause)
                                               object:nil];

    [self performSelector:@selector(editingDidPause)
               withObject:nil
               afterDelay:2.0];
}

- (void)editingDidPause
{
    dispatch_async(dispatch_get_main_queue(), ^{
      if (self.controlTextPausedBlock) {
        self.controlTextPausedBlock();
      }
    });
}

- (void)setControlTextPausedBlock:(void (^)())controlTextPausedBlock
{
    objc_setAssociatedObject(self, @selector(controlTextPausedBlock),
                             controlTextPausedBlock,
                             OBJC_ASSOCIATION_COPY_NONATOMIC);
}

- (void (^)())controlTextPausedBlock
{
    return objc_getAssociatedObject(self, @selector(controlTextPausedBlock));
}

@end