Supervisor child pid

[Zsolt Laky]

Thanks for your suggestion Roger, however get_child_spec/2 does not give the Pid for the child back.
Zsolt

> On Mar 3, 2020, at 9:54 PM, Roger Lipscombe <roger@REDACTED> wrote:
> 
> supervisor:get_child_spec/2 seems less brittle and more understandable.
> 
> On Tue, 3 Mar 2020 at 19:51, Zsolt Laky <zsoci@REDACTED> wrote:
>> 
>> Dear Team,
>> 
>> Finding a child Pid under a supervisor can be costly with the suggestion I found on the net with supervisor:which_children/1 as with a high number of children it returns a huge list with {Id, Child, Type, Modules} to find the MyChildId in.
>> 
>> What I did is:
>> 
>> -spec lookup(Name) -> Result when
>> Name   :: term(),
>> Result :: {ok, pid()} | {error, not_registered}.
>> lookup(Name) ->
>> FakeChild = #{ id => Name,
>>                start => {?MODULE, ignore_start_child, []},
>>                restart => temporary,
>>                shutdown => 2000,
>>                type => worker,
>>                modules => dynamic},
>> case supervisor:start_child(actor_sup, FakeChild) of
>>   {error, {already_started, Pid}} ->
>>     {ok, Pid};
>>   _Else -> %% {error, {ignored, _}}
>>     {error, not_registered}
>> end.
>> 
>> -spec ignore_start_child() ->
>> {error, ignored}.
>> ignore_start_child() ->
>> {error, ignored}.
>> 
>> I ask the experts if they see any pitfall I might have missed.
>> 
>> Thanks in advance and kind regards,
>> Zsolt