Refine Objective-C frameworks for Swift

4:43 - Describe nullability to control optionals (method and property annotations)

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

@interface SKMission : NSObject

@property (readonly, nullable) NSString *name;

- (nonnull instancetype)initWithName:(nullable NSString *)name;

@end

6:53 - Describe nullability to control optionals (ASSUME_NONNULL blocks)

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKMission : NSObject

@property (readonly, nullable) NSString *name;

- (instancetype)initWithName:(nullable NSString *)name;

@end

NS_ASSUME_NONNULL_END

7:14 - Describe nullability to control optionals (qualifiers)

//
// Misc.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NSString * _Nonnull const SKRocketSaturnV;

@interface ResourceValueContainer : NSObject

- (BOOL)getResourceValue:(id _Nullable * _Nonnull)outValue error:(NSError**)error;

@end

8:09 - Finding nullability mistakes with Objective-C tools

//
// SKMission.h
//

#import <Foundation/Foundation.h>

@interface SKMission : NSObject

@property (strong, nonnull) NSString *rocket;
@property (strong, nonnull) NSString *capsule;

@end

//
// SKRocket.h
//

#import <Foundation/Foundation.h>

extern NSString *_Nonnull const SKRocketSaturnV;

// 
// SKMission.m
//
// Try building this file and then try analyzing it.
//

#import "SKRocket.h"
#import "SKMission.h"

@implementation SKMission @end

@interface SKMissionConfigurator : NSObject

@property (strong, nullable) SKMission *mission;

@end

@implementation SKMissionConfigurator

- (void)testBadUseWithWarning {
    [self.mission setCapsule:nil];
}

- (void)testBadUseWithStaticAnalyzer:(BOOL)missionIsSkylab1 {
    NSString *capsule = nil;

    if (!missionIsSkylab1) {
        capsule = SKCapsuleApolloCSM;
    }
    
    self.mission.capsule = capsule;
}

@end

11:07 - Use Objective-C generics for Foundation types

//
// SKAstronaut.h
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKAstronaut : NSObject
// Stub declaration
@end

NS_ASSUME_NONNULL_END

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>
#import <SpaceKit/SKAstronaut.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKMission : NSObject

@property (readonly) NSArray<SKAstronaut *> *crew;

@end

NS_ASSUME_NONNULL_END

11:33 - Use Int for numbers—unsigned types are for bitwise operations

//
// SKRocket.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

NSInteger SKRocketStageCount(NSString *);

NS_ASSUME_NONNULL_END

//
// NSData+xor.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

@interface NSData (xor)

- (void)xorWithByte:(uint8_t)value;

@end

13:23 - Strengthen stringly-typed constants

//
// SKRocket.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

typedef NSString *SKRocket NS_STRING_ENUM;

extern SKRocket const SKRocketAtlas;
extern SKRocket const SKRocketTitanII;
extern SKRocket const SKRocketSaturnIB;
extern SKRocket const SKRocketSaturnV;

NSInteger SKRocketStageCount(SKRocket);

NS_ASSUME_NONNULL_END

15:24 - Specify initializer behavior

//
// SKAstronaut.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKAstronaut : NSObject

- (instancetype)initWithNameComponents:(NSPersonNameComponents *)name NS_DESIGNATED_INITIALIZER;
- (instancetype)initWithName:(NSString *)name;
- (instancetype)init NS_UNAVAILABLE;

@property (strong, readwrite) NSPersonNameComponents *nameComponents;
@property (readonly) NSString *name;

@end

NS_ASSUME_NONNULL_END

// 
// SKAstronaut.m
// 

#import "SKAstronaut.h"

@interface SKAstronaut ()
@property (class, readonly, strong) NSPersonNameComponentsFormatter *nameFormatter;
@end

@implementation SKAstronaut

- (id)initWithNameComponents:(NSPersonNameComponents *)name {
    self = [super init];
    if (self) {
        _name = name;
    }
    return self;
}

- (id)initWithName:(NSString *)name {
    return [self initWithNameComponents:[SKAstronaut _componentsFromName:name]];
}

- (id)init {
  [self doesNotRecognizeSelector:_cmd];
  return nil;
}

- (NSString *)name {
    return [SKAstronaut.nameFormatter stringFromPersonNameComponents:self.nameComponents];
}

+ (NSPersonNameComponents*)_componentsFromName:(NSString*)name {
    return [self.nameFormatter personNameComponentsFromString:name];
}

+ (NSPersonNameComponentsFormatter *)nameFormatter {
    static NSPersonNameComponentsFormatter *singleton;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        singleton = [NSPersonNameComponentsFormatter new];
    });
    return singleton;
}

@end

20:00 - Follow the error handling convention

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKMission : NSObject

/// \returns \c YES if saved; \c NO with non-nil \c *error if failed to save;
///          \c NO with nil \c *error` if nothing needed to be saved.
- (BOOL)saveToURL:(NSURL *)url error:(NSError **)error NS_SWIFT_NOTHROW DEPRECATED_ATTRIBUTE;

/// @param[out] wasDirty If provided, set to \c YES if the file needed to be
///   saved or \c NO if there weren’t any changes to save.
- (BOOL)saveToURL:(NSURL *)url wasDirty:(nullable BOOL *)wasDirty error:(NSError **)error;

@end

NS_ASSUME_NONNULL_END

22:40 - Refine an Objective-C API for Swift users

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKMission : NSObject

/// \returns \c YES if saved; \c NO with non-nil \c *error if failed to save;
///          \c NO with nil \c *error` if nothing needed to be saved.
- (BOOL)saveToURL:(NSURL *)url error:(NSError **)error NS_SWIFT_NOTHROW DEPRECATED_ATTRIBUTE;

/// @param[out] wasDirty If provided, set to \c YES if the file needed to be
///   saved or \c NO if there weren’t any changes to save.
- (BOOL)saveToURL:(NSURL *)url wasDirty:(nullable BOOL *)wasDirty error:(NSError **)error NS_REFINED_FOR_SWIFT;

@end

NS_ASSUME_NONNULL_END

// 
// SwiftExtensions.swift
//

import Foundation

extension SKMission {
    public func save(to url: URL) throws -> Bool {
        var wasDirty: ObjCBool = false
        try self.__save(to: url, wasDirty: &wasDirty)
        return wasDirty.boolValue
    }
}

31:35 - Fix method names with NS_SWIFT_NAME

//
// SKMission.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>
#import <SKAstronaut/SKAstronaut.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKMission : NSObject

- (NSSet<SKMission *> *)previousMissionsFlownByAstronaut:(SKAstronaut *)astronaut NS_SWIFT_NAME(previousMissions(flownBy:));

@end

33:12 - Rename and rework value types with NS_SWIFT_NAME

//
// SKFuelKind.h
//
// View the generated interface to see how Swift imports this header.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface SKFuel : NSObject
// Stub class
@end

typedef NS_ENUM(NSInteger, SKFuelKind) {
    SKFuelKindH2 = 0,
    SKFuelKindCH4 = 1,
    SKFuelKindC12H26 = 2
} NS_SWIFT_NAME(SKFuel.Kind);

NSString *SKFuelKindToNSString(SKFuelKind kind)
    NS_SWIFT_NAME(getter:SKFuelKind.description(self:));

35:59 - Add conformances to Objective-C types using custom Swift code

extension SKFuel.Kind: CustomStringConvertible {}

37:02 - Improve error code enums

//
//  SKError.h
//  SpaceKit
//

#import <Foundation/Foundation.h>

extern NSString *const SKErrorDomain;

typedef NS_ERROR_ENUM(SKErrorDomain, SKErrorCode) {
    SKErrorLaunchAborted = 1,
    SKErrorLaunchOutOfRange,
    SKErrorRapidUnscheduledDisassembly,
    SKErrorNotGoingToSpaceToday
};