为什么NSNumber比较方法不同？

Question

I used NSNumber class.

but methods that can use is different in follow environments.

First is a picture in command line tool environment. (Mac os x)

Second is a picture in single view application environment. (iOS)

: Can't use isGreaterThan:, isGreaterThanOrEqualTo:, isLessThan:.. Etc. methods

Why did that?

1] first picture

2] second picture

Answer 1

Those methods you're seeing on the Mac aren't actually part of the NSNumber class but instead are part of an informal protocol called NSComparisonMethods that is only available on Mac OS X. The methods in this protocol are convenience methods that actually just use the compare: method already available on many Cocoa classes. If you wanted, you could implement these methods as a category on NSNumber quite easily. Here is how I would implement -isGreaterThanOrEqualTo: .

@interface NSNumber (ConvenientComparison)

- (BOOL)isGreaterThanOrEqualTo:(id)object;

@end

@implementation NSNumber (ConvenientComparison)

- (BOOL)isGreaterThanOrEqualTo:(id)object
{
    if (![object isKindOfClass:[NSNumber class]])
    {
        // Not sure what NSNumber does if you pass in something that isn't a number.
        // Handle this case
        return NO;
    }

    NSNumber *numberToCompareAgainst = (NSNumber *)object;

    NSComparisonResult comparisonResult = [self compare:numberToCompareAgainst];

    if (comparisonResult == NSOrderedSame || comparisonResult == NSOrdereedDescending)
        return YES;

    return NO;
}

Answer 2

Those methods are part of the NSComparisonMethods protocol, which exists on the Mac but not on iOS. As for why it doesn't exist on iOS: It's part of Cocoa's scripting support, which did not get ported to iOS since AppleScript and OSA don't exist there.

Answer 3

I am not sure of why there is a difference. I checked the documentation for ios 5.0 and OS X 10.6. They both don't have the isGreater... methods.

You can compare your NSNumber s using

- (NSComparisonResult)compare:(NSNumber *)aNumber

NSComparisonResult compResult = [test compare:aNumber];

and check for test >= aNumber

if (compResult == NSOrderedDescending || compResult == NSOrderedSame) {

}

Return Value NSOrderedAscending if the value of aNumber is greater than the receiver's, NSOrderedSame if they're equal, and NSOrderedDescending if the value of aNumber is less than the receiver's.