block中多重引用

device.connect({ [weak self] (tmpDevice, success) in
     guard let self = self else { return }
     if success {
            // 连接成功
            device.discoverCharacteristics(for: self.Service_UUID) { (success) -> (Void) in
                        if success {
                            device.subscribe(forService: self.Service_UUID, characteristic: self.NOTIFY_Characteristic_UUID) { (device, serviceData, characterData, success) in
                                if let completion = completion {
                                    completion(device, true)
                                }
                            }
                            device.readCharacteristicCallback = ({ [weak self] (characteristic, model) in
                                if let model = model {
                                    self?.receiveNotifyModel(model: model)
                                }
                            })
                        }
                        else {
                            self.connectToDevice(device: device, curCount: curCount - 1, completion)
                        }
                    }
                }
                else {
                    self.connectToDevice(device: device, curCount: curCount - 1,completion)
                }
            })

在第一重block中如果使用了

guard let self = self else { return }

那么接下来的内部的每一重block，用到的self都是强指针，都要使用[weak self]防止强引用。

如果第一重block中，只使用了[weak self],不使用

guard let self = self else { return }

那么后面的block中也没必要使用[weak self],否则会出错。