Errors

Every method in a Hybrid Object can throw an error using the language-default error throwing feature:

Swift

HybridMath.swift

class HybridMath : HybridMathSpec {
  public func add(a: Double, b: Double) throws -> Double {
    if a < 0 || b < 0 {
      throw RuntimeError.error("Value cannot be negative!")
    }
    return a + b
  }
}

Kotlin

HybridMath.kt

class HybridMath : HybridMathSpec() {
  override fun add(a: Double, b: Double): Double {
    if (a < 0 || b < 0) {
      throw Error("Value cannot be negative!")
    }
    return a + b
  }
}

C++

HybridMath.hpp

class HybridMath: public HybridMathSpec {
  double add(double a, double b) override {
    if (a < 0 || b < 0) {
      throw std::runtime_error("Value cannot be negative!");
    }
    return a + b;
  }
};

Errors will be propagated upwards to JS and can be caught just like any other kind of error using try/catch:

`Math.add(...)`: Value cannot be negative!

Promise rejections

Promises can also be rejected using error throwing syntax on the native side:

Swift

HybridMath.swift

class HybridMath : HybridMathSpec {
  public func add(a: Double, b: Double) throws -> Promise<Double> {
    return Promise.async {
      if a < 0 || b < 0 {
        throw RuntimeError.error("Value cannot be negative!")
      }
      return a + b
    }
  }
}

Kotlin

HybridMath.kt

class HybridMath : HybridMathSpec() {
  override fun add(a: Double, b: Double): Promise<Double> {
    return Promise.async {
      if (a < 0 || b < 0) {
        throw Error("Value cannot be negative!")
      }
      return@async a + b
    }
  }
}

C++

HybridMath.hpp

class HybridMath: public HybridMathSpec {
  std::future<double> add(double a, double b) override {
    return std::async(std::launch::async, [=]() -> double {
      if (a < 0 || b < 0) {
        throw std::runtime_error("Value cannot be negative!");
      }
      return a + b;
    });
  }
};

Promise rejections are handled as usual using the .catch, or await/catch syntax in JS:

const math = // ...
try {
  await math.add(-5, -1)
} catch (error) {
  console.log(error)
}

Swift Errors

Due to a Swift compiler bug, Swift Hybrid Objects can currently not throw errors. Instead, they will raise a fatalError(..) which can only be seen if the app is running in Xcode (debugger). This should be fixed in the next Xcode version.