[Pythonmac-SIG] PyObjC and Criollo HTTP server

[Ronald Oussoren]

So much for typing code in Mail.app…. “Retail” should be “retval”. 

Ronald
—

Twitter: @ronaldoussoren
Blog: https://blog.ronaldoussoren.net/

> On 6 Jan 2020, at 15:27, Ronald Oussoren via Pythonmac-SIG <pythonmac-sig at python.org> wrote:
> 
> 
> 
>> On 6 Jan 2020, at 00:51, Rand Dvorak <randdvorak at gmail.com> wrote:
>> 
>> 
>> I am trying to implement a simple server in PyObjC for the Criollo HTTP server.  The server has a method to set route handlers by passing a block to setup the route and then when it receives and HTTP request for the route it calls the block.  The block has the signature:
>> 
>> typedef void(^CRRouteBlock)(CRRequest* _Nonnull request, CRResponse* _Nonnull response, CRRouteCompletionBlock _Nonnull completionHandler);
>> 
>> 
>> So, here is my simple proof of concept:
>> 
>> import objc 
>> CRApplication = objc.lookUpClass("CRApplication")
>> global server
>> 
>> def helloHandler(self, request, response, handler):
>> 	response.send_("Hello World!")
>> 	handler()
>> 	
>> if __name__ == "__main__":
>> 	server = CRApplication.sharedApplication().delegate().server()
>> 	server.get_block_("/", objc.selector(helloHandler, signature=b'v@:@@@‘))  *** error occurs here
>> 	server.startListening()
>> 
>> 
>> But, when I try to setup the route I get the following error:
>> 
>> Traceback (most recent call last):
>> File "main.py", line 21, in <module>
>>   server.get_block_("/", objc.selector(helloHandler, signature=b'v@:@@'))
>> TypeError: Argument 3 is a block, but no signature available
>> 
>> 
>> Any ideas how to workaround this issue and implement the route handlers in PyObjC?
> 
> The code below should do the trick, but eas typed directly into this mail and might therefore contain syntax errors.
> 
> import objc
> objc.registerMetaDataForSelector(
>    b”CRApplication”,  # name of the class implementing “get_block:”, or “NSObject”
>    b”get_block:”,
>   {
>     “arguments”: {
>       2: {
>         “callable”: {
>          “arguments”: {
>           0: { “type”: b”^v” },
>           1: { “type”: b”@” },
>           2: { “type”: b”@” },
>           3: { “type”: b”@” }
>          },
>          “retail”: { “type”: b”v” }
>        } 
>      }
>   }
> )
> 
> This tells the bridge the signature for the block argument of the “get_block:” selector, which is information that cannot be retrieved from the Objective-C runtime. Argument 2 is the first real argument of ObjC selectors, after the implicit arguments “self” and “_imp” (which is not available in python code).
> 
> Ronald
> —
> 
> Twitter: @ronaldoussoren
> Blog: https://blog.ronaldoussoren.net/ <https://blog.ronaldoussoren.net/>
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