iOS判断对象是否为空需考虑4种情况

给NSObject写个分类,方便用

@interface NSObject (additions)
/**
 *  判断对象是否为空
 *  PS：nil、NSNil、@""、@0 以上4种返回YES
 *
 *  @return YES 为空  NO 为实例对象
 */
+ (BOOL)dx_isNullOrNilWithObject:(id)object;
@end

+ (BOOL)dx_isNullOrNilWithObject:(id)object;
{
    if (object == nil || [object isEqual:[NSNull null]]) {
        return YES;
    } else if ([object isKindOfClass:[NSString class]]) {
        if ([object isEqualToString:@""]) {
            return YES;
        } else {
            return NO;
        }
    } else if ([object isKindOfClass:[NSNumber class]]) {
        if ([object isEqualToNumber:@0]) {
            return YES;
        } else {
            return NO;
        }
    }
    
    return NO;
}