Singleton: Difference between revisions
→{{header|Phix}}
Line 1,646:
method instance { $instance; }
}</lang>
=={{header|Phix}}==
Not really any special handling for singletons in Phix, but you can do something like this,
or keep check() private and invoke it internally from a few critical routines.
Needs 0.8.1+
<lang Phix>-- <separate include file>
object chk = NULL
class singleton
public procedure check()
if chk==NULL then
chk = this
elsif this!=chk then
?9/0
end if
?"ok"
end procedure
end class
global singleton s = new()
--global singleton s2 = new()
-- </separate include file>
s.check()
--s2.check() -- dies</lang>
While all classes are technically global in the sense that builtins\structs.e knows all about them, the
implicit associated user defined type is by default private (ie w/o "global" in front of the class def).
The above separate file prohibits the use of (other) <code>singleton s = new()</code> everywhere, however
<code>class s = new("singleton")</code> could still be used anywhere, and that way get duplicates.
One obvious alternative (of no special merit imo) might be to replace that global singleton s with:
<lang Phix>global function get_singleton()
if chk==NULL then
chk = new("singleton")
end if
return chk
end function</lang>
Technically, builtins/struct.e looks like it could easily be modified to support something very similar
to the Python Borg pattern, by appropriately sharing cdx/tid in new(). However it would be even better
to share the whole delete_routine()'d res, and that would probably be best achieved by setting a new
flag, say S_SINGLETON or S_STATIC, alongside and triggered via similar syntax to S_ABSTRACT/S_NULLABLE.
Maybe.
=={{header|PHP}}==
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