Re: Exposure of nil to end-users

[Ben Harper <rogojin@...>]

Hmm thanks guys..

The idea of making a special 'NULL' type sounds best - think I'll go with that.


On Thu, Feb 5, 2009 at 12:30 PM, steve donovan
<steve.j.donovan@gmail.com> wrote:
> This is the famous 'nullable type' problem.
>
> One option is for the database layer never to return nil in the case
> of a NULL field, but "" or 0 depending on the type of the field.
>
> Another option is to make a special Null object which has default
> string-like and number-like semantics. But this is tricky to do
> properly, since you'd need to define methods like 'null:sub(1,1)' etc
> as well as override __concat, __add, etc.
>
> steve d.
>
> On Thu, Feb 5, 2009 at 12:05 PM, Ben Harper <rogojin@gmail.com> wrote:
>> I am using Lua as a language that allows end-users to manipulate
>> database records.
>> My problem is that I'm not sure how to expose NULL values to the user.
>>
>> In this example, value = nil
>> User Types:      value .. "abc"
>> User Expects:   'abc'
>> User Gets:        Error: attempt to concatenate a nil value
>>
>> Has anybody had a similar problem, and how have you dealt with it?
>>
>> Thanks,
>> Ben
>>
>