ClassA does not work as expected, ClassB does. Sample code for: http://stackoverflow.com/questions/35590015/swift-objc-circular-import

CircularImports-Bridging-Header.h

//
//  Use this file to import your target's public headers that you would like to expose to Swift.
//

#import "XXClassC.h"

ClassA+B.swift

//
//  ClassA+B.swift
//

import Foundation

/**
 Create contrived class that is named XXClassA in ObjC and ClassA in Swift.
 */
@objc(XXClassA) class ClassA: NSObject {
    let foo = "bar"
}

/**
 Create contrived class that is named XXClassB in ObjC and Swift.
 */
class XXClassB: NSObject {
    let foo = "bar"
}



extension ClassA {
    /**
     Attempt to instantiate XXClassC (which has a reference to XXClassA) from Swift fails.
     -Note: Implemented in extension for clarity of post, but same issue arises if part of main class.
     */
    func useClassC() {
        let someVar1 = XXClassC(a: XXClassA())  // Error: use of unresolved identifier 'XXClassA'
        let someVar2 = XXClassC(b: XXClassB())  // works
    }
}

XXClassC.h

//
//  XXClassC.h
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@class XXClassA, XXClassB;

@interface XXClassC : NSObject

-(instancetype)initWithA:(XXClassA *)classA;
-(instancetype)initWithB:(XXClassB *)classB;

// mark default init as unnavailable
-(instancetype)init __attribute__((unavailable));

@end

NS_ASSUME_NONNULL_END

XXClassC.m

//
//  XXClassC.m
//

#import "XXClassC.h"
#import "CircularImports-swift.h"

NS_ASSUME_NONNULL_BEGIN

@implementation XXClassC

- (instancetype)initWithA:(XXClassA *)classA {
    NSLog(@"%@", classA.foo);
    return [super init];
}

- (instancetype)initWithB:(XXClassB *)classB {
    NSLog(@"%@", classB.foo);
    return [super init];
}

@end

NS_ASSUME_NONNULL_END