For-in loop and why it stops

I’m new Swift. The below exercise is teaching me how to assign multiple return values to a function. But it’s the for-in loop that’s confusing me. When I learned about these, the exercises always looped through all the possibilities in the array and then every…

Data and String in Swift3

I’m developing a very small iOS application in Swift 3, and I want to interact via wifi with my RPi,using a Simple Socket Server method.   Here in this part of program,       @IBAction func ButtoniPhone(_ sender: Any) {               let data :…

dyld: Symbol not found: _OBJC_CLASS_$_MTLToolsArgumentEncoder

When I used xcode 9.0 beta 3   to  compile scenekit and metal codes for drawing , I run xcode in debug mode, I met a crash as follows: dyld: Symbol not found: _OBJC_CLASS_$_MTLToolsArgumentEncoder   Referenced from: /Developer/Library/PrivateFrameworks/MTLToolsDeviceSupport.framework/libMTLInterpose.dylib   Expected in: /System/Library/PrivateFrameworks/MetalTools.framework/MetalTools in /Developer/Library/PrivateFrameworks/MTLToolsDeviceSupport.framework/libMTLInterpose.dylib I end…