数据处理

1.判空处理

+ (BOOL)isNull:(id)string {     if ([string isEqual:@"NULL"] || [string isKindOfClass:[NSNull class]] || [string isEqual:[NSNull null]] || [string isEqual:NULL] || [[string class] isSubclassOfClass:[NSNull class]] || string == nil || string == NULL || [string isKindOfClass:[NSNull class]] || [[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length]==0 || [string isEqualToString:@"<null>"] || [string isEqualToString:@"(null)"]) {         return NO;     } else {         return YES;     } }