Handling Java Exceptions from Swift

[trei...@gmail.com]

Hi,

I'm currently building an iOS app in Swift binding to a shared Java library I transcode with j2objc.

Some of the Java code I'm translating with throws exceptions. These seem to be correctly translated into Objective-C. Eg,

this Java:

public void thrower() throws IllegalArgumentException {
    throw new IllegalArgumentException("message");
}

results in:

- (void)thrower {
  @throw new_JavaLangIllegalArgumentException_initWithNSString_(@"message");
}
But it seems that NSExceptions aren't meant to be handled from Swift code and the convention to deal with this is to make ObjC functions return nil or boolean and set an optional NSError** argument as described here:

https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ErrorHandlingCocoa/CreateCustomizeNSError/CreateCustomizeNSError.html

I believe this is also what was suggested here:

https://groups.google.com/forum/#!searchin/j2objc-discuss/exception|sort:date/j2objc-discuss/dSbz2J13Z-U/TeH0lXUECQAJ

The following code seems like it would convert NSException to NSError to support try-catch blocks in Swift:

https://stackoverflow.com/a/36454808

How would I do the equivalent for Java exceptions? Just replace NSException with JavaLangException?

Is there a simpler way to handle this?

Thanks again!

[trei...@gmail.com]

On Friday, November 8, 2019 at 2:43:57 PM UTC-8, trei...@gmail.com wrote:

The following code seems like it would convert NSException to NSError to support try-catch blocks in Swift:

https://stackoverflow.com/a/36454808

How would I do the equivalent for Java exceptions? Just replace NSException with JavaLangException?

I tried this and it seems to work as expected. 

[Tom Ball]

Awesome! Would you like to be a guest blogger at https://j2objc.blogspot.com/ and describe this? It seems like it would be very useful to other developers in the future.

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[trei...@gmail.com]

I would love to! Please see my direct mail for my first draft.

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[trei...@gmail.com]

And now it's published: https://j2objc.blogspot.com/2019/11/catching-java-exceptions-in-swift-via.html