WIP Swift bug report.

gistfile1.txt

If you construct a Swift NSObject subclass with a designated initialiser that only has default parameters, for example;

{code:swift}
class SomeClass: NSObject {
    private let foo: Int!
    
    init(foo bar: Int = 1) {
        foo = bar
    }
}
{code}

… you can use the initialiser without any parameters, e.g.;

{code}
SomeClass() // Works fine
{code}

However, if you then try create this class in an Objective-C file with the `+new` method, you get a fatal error at runtime instead of a compile time error. This;

{code}
#import <Foundation/Foundation.h>
#import "InitTestProject-Swift.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"Hello, World!");
        
        [SomeClass new]; // No compiler warning.
    }
    return 0;
}
{code}

… results in;

{code}
fatal error: use of unimplemented initializer 'init()' for class 'InitTestProject.SomeClass'
Program ended with exit code: 9
{code}

---

`[[SomeClass alloc] init]` gives a compiler warning, which now makes sense. `+new` uses `alloc init` to create new instances and the exact `init()` without _any_ parameters hasn't actually been implemented.

However, the intent for creating a designated initialiser with only default parameters if for it to be initialised easily. In Swift this works great (e.g. `SomeClass()`). But in Objective-C, one might want `[[SomeClass alloc] init]` and especially `[SomeClass new]` to also work out of the box.

For the implementation, you could check whether the parameters of an NSObject subclass designated initialiser all have defaults, and if so create a convenience initialiser `init()`. That would call the original with all the parameters filled in.

Sample project: https://github.com/SpacyRicochet/InitTestProject