NSRunLoop+Condition.h

#import <Foundation/Foundation.h>

@interface NSRunLoop (Condition)

-(BOOL)runInDefaultModeWhileCondition:(BOOL *)condition inIntervals:(NSTimeInterval) quantum;

-(BOOL)runWhileCondition:(BOOL *)condition inMode:(NSString *)mode inIntervals:(NSTimeInterval) quantum;

@end

NSRunLoop+Condition.m

#import "NSRunLoop+Condition.h"

@implementation NSRunLoop (Condition)

-(BOOL)runInDefaultModeWhileCondition:(BOOL *)condition inIntervals:(NSTimeInterval) quantum {
    return [self runWhileCondition:condition inMode:NSDefaultRunLoopMode inIntervals:quantum];
}

-(BOOL)runWhileCondition:(BOOL *)condition inMode:(NSString *)mode inIntervals:(NSTimeInterval) quantum {
    BOOL didRun = NO;
    BOOL shouldRun = YES;
    NSPort *dummyPort = [NSMachPort port];
    [self addPort:dummyPort forMode:NSDefaultRunLoopMode];
    while (shouldRun) {
        @autoreleasepool {
            didRun = [self runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:quantum]];
            shouldRun = (didRun ? *condition : NO);
        }
    }
    [self removePort:dummyPort forMode:NSDefaultRunLoopMode];
    return didRun;
}

@end

This is BSD Licensed