I need a globally accessible AA of type string[string] and find that it won't compile unless I use the static this(){} method as described in this thread:

http://forum.dlang.org/thread/owhfdwrpfuiehzpiuqux@forum.dlang.org#post-mailman.1522.1346449072.31962.digitalmars-d-learn:40puremagic.com

I understand the concept of this() insofar as returning a reference to an object but what is 'this' in the context referred to? A reference to the module??

It doesn't seem very intuitive (to me at least!) especially given that strings are immutable anyway.

Paul

On 2015-06-06 20:18, Paul wrote:
> I need a globally accessible AA of type string[string] and find that it
> won't compile unless I use the static this(){} method as described in
> this thread:
>
> http://forum.dlang.org/thread/owhfdwrpfuiehzpiuqux@forum.dlang.org#post-mailman.1522.1346449072.31962.digitalmars-d-learn:40puremagic.com
>
>
> I understand the concept of this() insofar as returning a reference to
> an object but what is 'this' in the context referred to? A reference to
> the module??

"static this" is a module constructor. It's run before the "main" function is run.

-- 
/Jacob Carlborg

On Saturday, June 06, 2015 18:18:07 Paul via Digitalmars-d-learn wrote:
> I need a globally accessible AA of type string[string] and find that it won't compile unless I use the static this(){} method as described in this thread:
>
> http://forum.dlang.org/thread/owhfdwrpfuiehzpiuqux@forum.dlang.org#post-mailman.1522.1346449072.31962.digitalmars-d-learn:40puremagic.com
>
> I understand the concept of this() insofar as returning a reference to an object but what is 'this' in the context referred to? A reference to the module??
>
> It doesn't seem very intuitive (to me at least!) especially given
> that strings are immutable anyway.

It's talking about static constructors, which are functions that run before main rather than being constructors which are tied to specific objects. If you search for "static constructor" on this page, you'll find some documentation on them:

http://dlang.org/class.html

Another place to read up on them would be Ali's book:

http://ddili.org/ders/d.en/modules.html

- Jonathan M Davis

On Saturday, 6 June 2015 at 19:07:58 UTC, Jonathan M Davis wrote:
> On Saturday, June 06, 2015 18:18:07 Paul via Digitalmars-d-learn wrote:
>> I need a globally accessible AA of type string[string] and find
>> that it won't compile unless I use the static this(){} method as
>> described in this thread:
>>
>> http://forum.dlang.org/thread/owhfdwrpfuiehzpiuqux@forum.dlang.org#post-mailman.1522.1346449072.31962.digitalmars-d-learn:40puremagic.com
>>
>> I understand the concept of this() insofar as returning a
>> reference to an object but what is 'this' in the context referred
>> to? A reference to the module??
>>
>> It doesn't seem very intuitive (to me at least!) especially given
>> that strings are immutable anyway.
>
> It's talking about static constructors, which are functions that run before
> main rather than being constructors which are tied to specific objects. If
> you search for "static constructor" on this page, you'll find some
> documentation on them:
>
> http://dlang.org/class.html
>
> Another place to read up on them would be Ali's book:
>
> http://ddili.org/ders/d.en/modules.html
>
> - Jonathan M Davis

Thanks both, that makes sense.

However, I now get an 'undefined identifier' error when compiling and trying to access the AA from a function within the same module.

static this()
{
  string[string] tagWords = [ 	"DIST" : "Distance", .....
}

...

  if(tag in tagWords)
  {
    retVal.tag = tagWords[tag]; <---- 'Error: undefined identifier tagWords'
    ...

According to Ali's book that looks like a linker message but I am compiling like so:

dmd -w oftest *.d

Do I need to qualify the name in some way or give DMD some more info?

On Saturday, 6 June 2015 at 20:30:50 UTC, Paul wrote:
> However, I now get an 'undefined identifier' error when compiling and trying to access the AA from a function within the same module.
>
> static this()
> {
>   string[string] tagWords = [ 	"DIST" : "Distance", .....
> }
>
> ...
>
>   if(tag in tagWords)
>   {
>     retVal.tag = tagWords[tag]; <---- 'Error: undefined identifier tagWords'
>     ...

You have to declare tagWords in module scope, but initialize it in the static constructor:

string[string] tagWords;
static this()
{
    tagWords = [ 	"DIST" : "Distance", .....
}

>
> According to Ali's book that looks like a linker message

Nope, that's not a linker message.

"undefined identifier" = compiler
"undefined reference" = linker

On Saturday, 6 June 2015 at 20:39:14 UTC, anonymous wrote:
> On Saturday, 6 June 2015 at 20:30:50 UTC, Paul wrote:
>> However, I now get an 'undefined identifier' error when compiling and trying to access the AA from a function within the same module.
>>
>> static this()
>> {
>>  string[string] tagWords = [ 	"DIST" : "Distance", .....
>> }
>>
>> ...
>>
>>  if(tag in tagWords)
>>  {
>>    retVal.tag = tagWords[tag]; <---- 'Error: undefined identifier tagWords'
>>    ...
>
> You have to declare tagWords in module scope, but initialize it in the static constructor:
>
> string[string] tagWords;
> static this()
> {
>     tagWords = [ 	"DIST" : "Distance", .....
> }
>
>>
>> According to Ali's book that looks like a linker message
>
> Nope, that's not a linker message.
>
> "undefined identifier" = compiler
> "undefined reference" = linker

Doh! Thank you anonymous person :D