https://www.jianshu.com/p/9591f1b8b7eb http://southpeak.github.io/2014/07/31/core-bluetooth-programming-guide-2/ printing-a-variable-memory-address-in-swift https://stackoverflow.com/questions/24058906/printing-a-variable-memory-address-in-swift ios-stay-connected-to-an-external-ble-device-as-much-as-possible https://medium.com/arkulpa/ios-stay-connected-to-an-external-ble-device-as-much-as-possible-699d434846d2 save-custom-objects-into-nsuserdefaults https://stackoverflow.com/questions/29986957/save-custom-objects-into-nsuserdefaults https://stackoverflow.com/questions/26469457/saving-custom-swift-class-with-nscoding-to-userdefaults https://stackoverflow.com/questions/29986957/save-custom-objects-into-nsuserdefaults https://stackoverflow.com/questions/44876420/save-struct-to-userdefaults ble autoreconnect http://muhlenxi.com/2017/07/07/About-Ble-Auto-Connecting/ how-to-compare-two-struct-objects https://stackoverflow.com/questions/46074718/how-to-compare-two-struct-...