Apple documentation advices against use of Objective-C and Swift in AudioUnit input or render callbacks. So the callbacks are written mostly in C where we can quickly copy data and pass that data to secondary thread for processing. To share variables between C and Objective C/Swift, the advice is to use inRefCon as a pointer to Controller object and then access it's variable. While it is easy in Objective C to simply use the following code in AudioUnit render callback function,
MyController *controller = (MyController *)inRefCon
if (controller->muteAudio) {
...
...
}
And this guaranteed that access to muteAudio is simply access to memory address (base address of controller + offset for muteAudio var) unlike full Objective C messaging. But I can't find an equivalent in Swift as Swift has no member variables, all vars are like properties. So I am not sure if the following is the right thing to do in Swift render callback :
let controller = unsafeBitCast(inRefCon, to: MyController.self) /
if !controller.muteAudio {
...
...
}
Doesn't controller.muteAudio trigger message passing in Swift rather than simple access to memory address (base address of controller + offset for muteAudio var)?
