Re: Swift closure isn't allowed to capture context

[Colin Morelli <colin.morelli@xxxxxxxxx>]

Hey Stefan,

This might not be entirely helpful to you depending on your use case, but I am using pjsip in a swift application. I actually ended up wrapping everything PJSIP in Objective-C. Interfacing with C code is much easier in Obj-C IMO (without the constant wrapping/unwrapping of UnsafeMutablePointers). The Swift <-> Obj-C interop is much more refined than Swift<->C.

That said, even in Objective-C you have to find a place to store context. In my application, my custom objective-c wrapper around calls/accounts is stored in the user data of the call with pjsua_call_set_user_data(callId, (__bridge void *) self);

Callbacks end up looking like:

static void onCallState(pjsua_call_id callId, pjsip_event *event) {

  void *data = "">

  if (data == NULL) {

    return;

  }

  

  @autoreleasepool {

    SBSCall *call = (__bridge SBSCall *) data;

    [call handleCallStateChange:event];

  }

}

I hope that's helpful in some way.

Best,

Colin

On Sat, Nov 12, 2016 at 3:32 PM Stefan Godoroja <mancunianetz@xxxxxx> wrote:

Hi guys,

Recently I was trying to use pjsip stack libraries in an iOS project which uses Swift language, but I have noticed
a thing which makes library hard to use. C function pointers are translated into Swift closures, a special type of closure. The problem is
that Swift doesn’t allow to capture context (self) in this type of closure. Looking into the source code of pjsip libs convinced me that
pjsip callbacks don’t have a parameter for referencing context. I’m not a C specialist but this seems to me at least not ok.

I’m addressing the developers who used library in Swift projects, how did you handle this situation ?



Best regards,
Stefan




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