可以寫個分類來處理

- (BOOL)blankString{
    if (![self isKindOfClass:[NSString class]] ){
        return  YES;
    }
    if ([self isEqual:[NSNull null]]){
        return  YES;
    }
    if (self == NULL || [self isEqual:nil] || [self isEqual:Nil] || self == nil){
        return  YES;
    }
    if([self
 
 isEqualToString:@"(null)"]){
        return  YES;
    }
    if([self isEqualToString:@"<null>"]){
        return  YES;
    }
    if (self.length == 0 || [[self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0){
        return  YES;
    }
    return
 
 NO;
}