ios - 我不明白为什么Objective-C委托(delegate)函数会起作用，而Swift委托(delegate)函数会崩溃。你能跟我解释一下吗？

我有一个用Objetive-C构建的框架。该框架用于连接蓝牙设备并与之交互。

在演示代码中，Objetive-C委托函数如下所示。该演示代码由框架的创建者提供。

-(void)babyScaleManagerScanDevices:(NSArray<ELBabyScaleDeviceModel *> *)babyScaleDevices{
    NSLog(@"babyScaleManagerScanDevices = %@",babyScaleDevices);
    ELBabyScaleDeviceModel *model = babyScaleDevices.firstObject;
}

我已经在快速项目中包含了该框架，并导入了标头。我正在尝试通过以下方法获得相同的结果：

func babyScaleManagerScanDevices(_ babyScaleDevices: [ELBabyScaleDeviceModel]?) {
    guard let device = babyScaleDevices?.first else {
      print("Error unwrapping first device")
      return
    }
    print("Device: \(String(describing: device))")
  }

我得到以下异常：

Thread 1: Precondition failed: NSArray element failed to match the Swift Array Element type
Expected ELBabyScaleDeviceModel but found ELPeripheralModel

Precondition failed: NSArray element failed to match the Swift Array Element type
Expected ELBabyScaleDeviceModel but found ELPeripheralModel: file /BuildRoot/Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-1100.2.274.2/swift/stdlib/public/core/ArrayBuffer.swift, line 354

检查babyScaleDevices数组显示：

babyScaleDevices    [ELBabyScaleDeviceModel]?   1 value some
[0] ELPeripheralModel * 0x281cae100 0x0000000281cae100

结果与Objetive-C和我的Swift项目中的演示代码相同。

类ELBabyScaleDeviceModel.h看起来像：

#import "ELPeripheralModel.h"

NS_ASSUME_NONNULL_BEGIN

@interface ELBabyScaleDeviceModel : ELPeripheralModel

@end

NS_ASSUME_NONNULL_END

您能解释一下发生了什么吗？

最佳答案

您必须将Array指定为NSArray

将此行添加到您的代码中

let devices = babyScaleDevices as NSArray

你可以试试这个

func babyScaleManagerScanDevices(_ babyScaleDevices: [ELBabyScaleDeviceModel]?) {
let devices = babyScaleDevices as NSArray
guard let device = devices.firstObject else {
    print("Error unwrapping first device")
    return
}
print("Device: \(String(describing: device))")

}

然后检查此-> Array vs NSArray