您使用什么类别的方法来使Cocoa编程更容易？

Question

我为Cocoa的内置类使用了一组类别方法,使我的生活更轻松.我将发布一些例子,但我真的想看看其他编码员提出了什么.你使用什么样的方便类别方法？

示例#1:

@implementation NSColor (MyCategories)
+ (NSColor *)colorWithCode:(long)code
{
    return [NSColor colorWithCalibratedRed:((code & 0xFF000000) >> 24) / 255.0
                                     green:((code & 0x00FF0000) >> 16) / 255.0
                                      blue:((code & 0x0000FF00) >>  8) / 255.0
                                     alpha:((code & 0x000000FF)      ) / 255.0];
}
@end

// usage:
NSColor * someColor = [NSColor colorWithCode:0xABCDEFFF];

示例#2:

@implementation NSView (MyCategories)
- (id)addNewSubViewOfType:(Class)viewType inFrame:(NSRect)frame
{
    id newView = [[viewType alloc] initWithFrame:frame];
    [self addSubview:newView];
    return [newView autorelease];
}
@end

// usage:
NSButton * myButton = [someView addNewSubviewOfType:[NSButton class]
                                            inFrame:someRect];

Answer 1

我真的很喜欢Andy Matuschak的" KVO + Blocks "类别NSObject.(是的,它在内部添加了一些新类作为实现细节,但最终结果只是一个类别NSObject).它允许您提供在符合KVO的值更改时执行的块,而不是必须处理方法中的每个 KVO观察observeValueForKeyPath:ofObject:change:context:.

Answer 2

我在 NSDate 上有一些漂亮的方法。这是不言自明的：

-(BOOL)isOnTheSameDayAsDate:(NSDate *)date {

    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateComponents *selfComponents = [cal components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit 
                                             fromDate:self];

    NSDateComponents *dateComponents = [cal components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit 
                                              fromDate:date];

    return (([selfComponents day] == [dateComponents day]) &&
            ([selfComponents month] == [dateComponents month]) && 
            ([selfComponents year] == [dateComponents year]));

}

用法：

if ([aDate isOnTheSameDayAsDate:anotherDate]) { ... }

这提供了一种轻松获取日期（例如“前一天上午 9 点”）的方法：

-(NSDate *)dateWithDayDelta:(NSInteger)daysBeforeOrAfter atHour:(NSUInteger)hour minute:(NSUInteger)minute second:(NSUInteger)second {

    NSDate *date = [self addTimeInterval:(24 * 60 * 60) * daysBeforeOrAfter];
    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDateComponents *comps = [calendar components:NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSHourCalendarUnit |         
                                                   NSMinuteCalendarUnit | NSSecondCalendarUnit 
                                      fromDate:date];

    [comps setHour:hour];
    [comps setMinute:minute];
    [comps setSecond:second];

    return [calendar dateFromComponents:comps];
}

用法：

// We want 9am yesterday
NSDate *nineAmYesterday = [[NSDate date] dateWithDayDelta:-1 
                                                   atHour:9 
                                                   minute:0 
                                                   second:0];