[erlang-questions] client in erlang server in objective C

Gianfranco Alongi <>
Wed Jul 18 14:29:23 CEST 2012


The Objective C mailing list is that way -->
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Cheers

On Wed, Jul 18, 2012 at 2:16 PM, Joe Armstrong <> wrote:
> On Wed, Jul 18, 2012 at 12:07 PM, Dmitry Klionsky <> wrote:
>> Decided to help you a little further:
>
> Thanks - I appreciate this ...
> I have a few more questions (inline)
>
>>
>> The problem is you can't just send("button", ...), because the "button" is
>> not a symbol, but a NSButton's class (or something like this) instance.
>> I'm not sure because I've never done any MacOX programming, but iOS.
>> And in order to send a message to an instance you need to know it. So, in
>> general, your workflow should be like this:
>>
>> Erlang side:
>> %% create button
>> send
>> {create_instance, {string, "NSButton"}}
>> receive
>> {ok, Instance}
>
> question 1:
> Is Instance an integer here? (see question 3)
>
>>
>> %% set button's title
>> send
>> {perform, {integer, Button} {string, "setTitle:"}, {string, "click me"}}
>
> Button is the integer in "Instance" above I assume
>
>> receive
>> ok
>>
>>
>> Objective-C side
>>
>> On receiving {create_instance, {string, Clazz}}:
>>
>> // note that `Class' is a reserved word
>> id instance = [[NSClassFromString(Clazz) alloc] init];
>> if (instance) {
>
>     What is instance? is this "really"  a 32 bit pointer?
>      How do I serialize it to send it back to erlang?
>
>
>>    reply {ok, instance};
>> } else {
>>    reply {error, @"No such class"}
>> }
>>
>> On receiving {perform, {integer, Instance}, {string, Selector}, {string,
>> Object}}:
>> SEL sel = NSSelectorFromString(Selector);
>> if (sel) {
>>    if ([Instance respondsToSelector(sel)]) {
>>          [Instance performSelector:sel withObject:Object];
>>       reply ok;
>>    } else {
>>         reply {error, @"No such selector"};
>>    }
>> } else {
>>   reply {error, @"Invalid selector"}
>> }
>
> Same question here. On the "wire" I'll see an encoding of
> {perform, {integer, Instance}, ... and so on How do I make an Objective
> C id or NSString from a sequence of bytes that I read from a socket.
> Also do I have to worry about strings (for example) being garbage collected.
>
> For example If I say (in objective C)
>
>      NSString s = @"hello"
>
> I create a literal string in the variable s
>
> But if I receive a string "hello" somewhere in a buffer from a socket
> I need to create a NSString and put it somewhere so it doesn't get
> garbage collected away. Something like:
>
>    NSMutableArray *stringtable = [[NSMutableArray alloc] init];
>
>     NSString s = [[NSString alloc] initWithString: Data]
>     [stringtable addObject:s];
>
> (Pardon my Objective C here - I'm a total beginner here)
>
>> This was a little messy, but hopefully you will get the idea.
>
> Yes - I get the idea, the problem is the nitty gritty details, not the idea.
> The idea is easy. Allocate some memory to store the stuff you received in
> create some dynamic objects and call some methods - problem is how.
>
> Thanks - I'll try this later
>
> /Joe
>
>>
>>
>>
>> On 07/18/2012 11:42 AM, Dmitry Klionsky wrote:
>>>
>>> Hi Joe,
>>>
>>> NSSelectorFromString, NSClassFromString and others are your friends here.
>>>
>>> For more detail have a look at:
>>>
>>> Objective-C Runtime Programming Guide
>>>
>>> https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Introduction/Introduction.html
>>>
>>> Objective-C Programming Language
>>>
>>> https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html
>>>
>>> Also I would also suggest you to evaluate the protobuffs. In my opinion
>>> the protobuffs are more concise and clear.
>>> There a couple of Objective-C implementations available:
>>> http://code.google.com/p/metasyntactic/wiki/ProtocolBuffers
>>> https://github.com/booyah/protobuf-objc
>>>
>>>
>>> Best regards,
>>> Dmitry Klionsky
>>>
>>>
>>> On 07/18/2012 11:10 AM, Joe Armstrong wrote:
>>>>
>>>> That's a very interesting idea. I haven't used thrift - but if the server
>>>> side code exists in Objective C this would be very interesting.
>>>>
>>>> (I tried to build thrift but the build failed :-)
>>>>
>>>>
>>>> I've now actually got an erlang client talking to an objective C
>>>> server - using AsnycSocket that Bob suggested but I can only exchange
>>>> strings.
>>>>
>>>> Now I need to figure out how to do build dynamic method calls in
>>>> objective C.
>>>>
>>>> In objective C I'd write
>>>>
>>>>       [button setTitle:@"click me"]
>>>>
>>>> In Erlang I'd like to encode this as a string
>>>> send it to objective C decode it and evaluate it.
>>>>
>>>> I'd like to do something like
>>>>
>>>>      send("button", "setTitle", [{string,"click me"}])
>>>>
>>>> In erlang
>>>>
>>>>     or to encode   [foo this:123 that:@"yea"] as
>>>>
>>>>     send("foo", "this:that", [{integer,123},{string,"yea"}])
>>>>
>>>> Then I'd like to serialize this as a string (in Erlang) and decode it
>>>> and evaluate it in Objective C
>>>>
>>>>      Any ideas how to do this?
>>>>
>>>> /Joe
>>>>
>>>>
>>>> On Tue, Jul 17, 2012 at 11:48 PM, Anthony Molinaro
>>>> <>  wrote:
>>>>>
>>>>> What about thrift http://thrift.apache.org/
>>>>>
>>>>> It's RPC style so you describe function calls, erlang clients are easy,
>>>>> the objective-c server would be generated for you (other than the
>>>>> body of the function).
>>>>>
>>>>> I've been using thrift to talk java->erlang and erlang->java, so
>>>>> talking erlang->objective-c should be straightforward.
>>>>>
>>>>> Some examples http://wiki.apache.org/thrift/ThriftUsageObjectiveC
>>>>>
>>>>> -Anthony
>>>>>
>>>>> On Sat, Jul 14, 2012 at 06:27:49PM +0200, Joe Armstrong wrote:
>>>>>>
>>>>>> I want the following:
>>>>>>
>>>>>>     - Client in erlang (easy)
>>>>>>    - Server in objective C (I'm thinking Mac OS-X lion - xcode 4.2 -
>>>>>> cocoa)
>>>>>>    -  socket communication
>>>>>>
>>>>>> [[ I'm a complete beginner with xcode/objective C ]]
>>>>>>
>>>>>> Has anybody written a simple objective C client that opens a port
>>>>>> waits for a message then executes a callback. This should be
>>>>>> non-blocking
>>>>>> and be integrated with the "standard" dispatcher top-loop.
>>>>>>
>>>>>> I'm confused by the profusion of classes that almost do this.
>>>>>>
>>>>>> Has anybody implemented this, or have pointers to a good place to
>>>>>> start.
>>>>>>
>>>>>> Cheers
>>>>>>
>>>>>> /Joe
>>>>>> _______________________________________________
>>>>>> erlang-questions mailing list
>>>>>> 
>>>>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>>>
>>>>> --
>>>>> ------------------------------------------------------------------------
>>>>> Anthony Molinaro<>
>>>>
>>>> _______________________________________________
>>>> erlang-questions mailing list
>>>> 
>>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>
>>>
>>>
>>
>>
>> --
>> Best regards,
>> Dmitry Klionsky
>>
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>> 
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