The first Apple Silicon Mac with the M1 chip is finally here. It seems that the pros and cons are swirling on the net.
I'm currently a Mac user, but rather than replacing my Mac, I'm looking at its potential application to satellite projects I'm working on. I expect that the image processing performance per price of the new Mac is extremely high, and the image processing performance per power consumption is also good. I will write about the artificial satellite project in Elixir Advent Calendar 2020, so please look forward to it.
So, instead of developing an iOS app or Mac app, using the mechanism to call the C program called NIF from Elixir, call the Swift code assets accumulated by Apple such as Core Image and Core ML from Elixir. I wrote this article with the aim of seeing if I could do it. If you can call Swift from Objective-C, you can call Objective-C from C, so you can also call Swift from Elixir.
Regarding Swift, except for the Apple Developer Program, there were only articles with old language specifications, so this article corresponding to Swift 5.3 adopted in Xcode 12.1, which is the latest Xcode as of 2020.11.12, is similar. I think there is something new about the article.
I'm also compiling Swift / Objective-C code using make on the command line instead of Xcode. I think the way to write Makefile is also helpful.
Share the code right away. It is published on GitHub with Apache-2.0 License.
https://github.com/zacky1972/swift_objc_test
Here's the Swift code I want to call:
ExampleClass.swift
import Foundation
@objc class ExampleClass: NSObject {
var count = 0
@objc func increment() {
count += 1
NSLog("increment")
}
@objc func increment(by amount: Int) {
count += amount
}
@objc func reset() {
count = 0
}
}
The source of this code is here. https://docs.swift.org/swift-book/LanguageGuide/Methods.html
To be able to call it from Objective-C, do the following two things.
import Foundation to derive from NSObject@ objc to the class and the method you want to call from Objective-C.The code on the Objective-C side looks like this.
main.m
#import <Foundation/Foundation.h>
#import "ExampleClass-Swift.h"
int main(int argc, char** argv)
{
ExampleClass *obj = [[ExampleClass alloc] init];
[obj increment];
NSLog(@"Testing");
}
The points are as follows:
ExampleClass, useimport "ExampleClass-Swift.h"(Import the header file with -Swift.h added to the class name)All you have to do is read it as Objective-C and call it normally.
The execution result is as follows.
% ./hello
2020-11-12 18:47:57.204 hello[10554:225821] increment
2020-11-12 18:47:57.204 hello[10554:225821] Testing
As expected, since the increment method was called earlier, it says Testing.
That's all the code to prepare.
Makefile
Let's take a look at the Makefile to see how to build it.
Makefile
.phony: all clean
all: hello
main.o: main.m ExampleClass-Swift.h
clang -c $< -o $@
ExampleClass.o: ExampleClass.swift ExampleClass-Swift.h
swiftc -emit-object -parse-as-library $<
ExampleClass-Swift.h: ExampleClass.swift
swiftc $< -emit-objc-header -emit-objc-header-path $@
hello: main.o ExampleClass.o
swiftc $^ -o $@ -framework Foundation
clean:
$(RM) hello *.o *.{swiftdoc,swiftmodule,swiftsourceinfo} ExampleClass ExampleClass-Swift.h
The points are as follows:
swiftc to compile Swift. Compile to an object file (.o) with the -emit-object and -parse-as-library options.clang to compile Objective-Cswiftc and specify -framework Foundation as the linker option.ExampleClass-Swift.h (header file given to Objective-C), use swiftc and the -emit-objc-header option. And use the -emit-objc-header-path option. Specify the path to the header file you want to generate immediately after the -emit-objc-header-path optionThe generated Objective-C header file is:
ExampleClass-Swift.h
// Generated by Apple Swift version 5.3 (swiftlang-1200.0.29.2 clang-1200.0.30.1)
#ifndef EXAMPLECLASS_SWIFT_H
#define EXAMPLECLASS_SWIFT_H
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgcc-compat"
#if !defined(__has_include)
# define __has_include(x) 0
#endif
#if !defined(__has_attribute)
# define __has_attribute(x) 0
#endif
#if !defined(__has_feature)
# define __has_feature(x) 0
#endif
#if !defined(__has_warning)
# define __has_warning(x) 0
#endif
#if __has_include(<swift/objc-prologue.h>)
# include <swift/objc-prologue.h>
#endif
#pragma clang diagnostic ignored "-Wauto-import"
#include <Foundation/Foundation.h>
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#if !defined(SWIFT_TYPEDEFS)
# define SWIFT_TYPEDEFS 1
# if __has_include(<uchar.h>)
# include <uchar.h>
# elif !defined(__cplusplus)
typedef uint_least16_t char16_t;
typedef uint_least32_t char32_t;
# endif
typedef float swift_float2 __attribute__((__ext_vector_type__(2)));
typedef float swift_float3 __attribute__((__ext_vector_type__(3)));
typedef float swift_float4 __attribute__((__ext_vector_type__(4)));
typedef double swift_double2 __attribute__((__ext_vector_type__(2)));
typedef double swift_double3 __attribute__((__ext_vector_type__(3)));
typedef double swift_double4 __attribute__((__ext_vector_type__(4)));
typedef int swift_int2 __attribute__((__ext_vector_type__(2)));
typedef int swift_int3 __attribute__((__ext_vector_type__(3)));
typedef int swift_int4 __attribute__((__ext_vector_type__(4)));
typedef unsigned int swift_uint2 __attribute__((__ext_vector_type__(2)));
typedef unsigned int swift_uint3 __attribute__((__ext_vector_type__(3)));
typedef unsigned int swift_uint4 __attribute__((__ext_vector_type__(4)));
#endif
#if !defined(SWIFT_PASTE)
# define SWIFT_PASTE_HELPER(x, y) x##y
# define SWIFT_PASTE(x, y) SWIFT_PASTE_HELPER(x, y)
#endif
#if !defined(SWIFT_METATYPE)
# define SWIFT_METATYPE(X) Class
#endif
#if !defined(SWIFT_CLASS_PROPERTY)
# if __has_feature(objc_class_property)
# define SWIFT_CLASS_PROPERTY(...) __VA_ARGS__
# else
# define SWIFT_CLASS_PROPERTY(...)
# endif
#endif
#if __has_attribute(objc_runtime_name)
# define SWIFT_RUNTIME_NAME(X) __attribute__((objc_runtime_name(X)))
#else
# define SWIFT_RUNTIME_NAME(X)
#endif
#if __has_attribute(swift_name)
# define SWIFT_COMPILE_NAME(X) __attribute__((swift_name(X)))
#else
# define SWIFT_COMPILE_NAME(X)
#endif
#if __has_attribute(objc_method_family)
# define SWIFT_METHOD_FAMILY(X) __attribute__((objc_method_family(X)))
#else
# define SWIFT_METHOD_FAMILY(X)
#endif
#if __has_attribute(noescape)
# define SWIFT_NOESCAPE __attribute__((noescape))
#else
# define SWIFT_NOESCAPE
#endif
#if __has_attribute(ns_consumed)
# define SWIFT_RELEASES_ARGUMENT __attribute__((ns_consumed))
#else
# define SWIFT_RELEASES_ARGUMENT
#endif
#if __has_attribute(warn_unused_result)
# define SWIFT_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
#else
# define SWIFT_WARN_UNUSED_RESULT
#endif
#if __has_attribute(noreturn)
# define SWIFT_NORETURN __attribute__((noreturn))
#else
# define SWIFT_NORETURN
#endif
#if !defined(SWIFT_CLASS_EXTRA)
# define SWIFT_CLASS_EXTRA
#endif
#if !defined(SWIFT_PROTOCOL_EXTRA)
# define SWIFT_PROTOCOL_EXTRA
#endif
#if !defined(SWIFT_ENUM_EXTRA)
# define SWIFT_ENUM_EXTRA
#endif
#if !defined(SWIFT_CLASS)
# if __has_attribute(objc_subclassing_restricted)
# define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_CLASS_EXTRA
# define SWIFT_CLASS_NAMED(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
# else
# define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
# define SWIFT_CLASS_NAMED(SWIFT_NAME) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
# endif
#endif
#if !defined(SWIFT_RESILIENT_CLASS)
# if __has_attribute(objc_class_stub)
# define SWIFT_RESILIENT_CLASS(SWIFT_NAME) SWIFT_CLASS(SWIFT_NAME) __attribute__((objc_class_stub))
# define SWIFT_RESILIENT_CLASS_NAMED(SWIFT_NAME) __attribute__((objc_class_stub)) SWIFT_CLASS_NAMED(SWIFT_NAME)
# else
# define SWIFT_RESILIENT_CLASS(SWIFT_NAME) SWIFT_CLASS(SWIFT_NAME)
# define SWIFT_RESILIENT_CLASS_NAMED(SWIFT_NAME) SWIFT_CLASS_NAMED(SWIFT_NAME)
# endif
#endif
#if !defined(SWIFT_PROTOCOL)
# define SWIFT_PROTOCOL(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) SWIFT_PROTOCOL_EXTRA
# define SWIFT_PROTOCOL_NAMED(SWIFT_NAME) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_PROTOCOL_EXTRA
#endif
#if !defined(SWIFT_EXTENSION)
# define SWIFT_EXTENSION(M) SWIFT_PASTE(M##_Swift_, __LINE__)
#endif
#if !defined(OBJC_DESIGNATED_INITIALIZER)
# if __has_attribute(objc_designated_initializer)
# define OBJC_DESIGNATED_INITIALIZER __attribute__((objc_designated_initializer))
# else
# define OBJC_DESIGNATED_INITIALIZER
# endif
#endif
#if !defined(SWIFT_ENUM_ATTR)
# if defined(__has_attribute) && __has_attribute(enum_extensibility)
# define SWIFT_ENUM_ATTR(_extensibility) __attribute__((enum_extensibility(_extensibility)))
# else
# define SWIFT_ENUM_ATTR(_extensibility)
# endif
#endif
#if !defined(SWIFT_ENUM)
# define SWIFT_ENUM(_type, _name, _extensibility) enum _name : _type _name; enum SWIFT_ENUM_ATTR(_extensibility) SWIFT_ENUM_EXTRA _name : _type
# if __has_feature(generalized_swift_name)
# define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME, _extensibility) enum _name : _type _name SWIFT_COMPILE_NAME(SWIFT_NAME); enum SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_ENUM_ATTR(_extensibility) SWIFT_ENUM_EXTRA _name : _type
# else
# define SWIFT_ENUM_NAMED(_type, _name, SWIFT_NAME, _extensibility) SWIFT_ENUM(_type, _name, _extensibility)
# endif
#endif
#if !defined(SWIFT_UNAVAILABLE)
# define SWIFT_UNAVAILABLE __attribute__((unavailable))
#endif
#if !defined(SWIFT_UNAVAILABLE_MSG)
# define SWIFT_UNAVAILABLE_MSG(msg) __attribute__((unavailable(msg)))
#endif
#if !defined(SWIFT_AVAILABILITY)
# define SWIFT_AVAILABILITY(plat, ...) __attribute__((availability(plat, __VA_ARGS__)))
#endif
#if !defined(SWIFT_WEAK_IMPORT)
# define SWIFT_WEAK_IMPORT __attribute__((weak_import))
#endif
#if !defined(SWIFT_DEPRECATED)
# define SWIFT_DEPRECATED __attribute__((deprecated))
#endif
#if !defined(SWIFT_DEPRECATED_MSG)
# define SWIFT_DEPRECATED_MSG(...) __attribute__((deprecated(__VA_ARGS__)))
#endif
#if __has_feature(attribute_diagnose_if_objc)
# define SWIFT_DEPRECATED_OBJC(Msg) __attribute__((diagnose_if(1, Msg, "warning")))
#else
# define SWIFT_DEPRECATED_OBJC(Msg) SWIFT_DEPRECATED_MSG(Msg)
#endif
#if !defined(IBSegueAction)
# define IBSegueAction
#endif
#if __has_feature(modules)
#if __has_warning("-Watimport-in-framework-header")
#pragma clang diagnostic ignored "-Watimport-in-framework-header"
#endif
@import ObjectiveC;
#endif
#pragma clang diagnostic ignored "-Wproperty-attribute-mismatch"
#pragma clang diagnostic ignored "-Wduplicate-method-arg"
#if __has_warning("-Wpragma-clang-attribute")
# pragma clang diagnostic ignored "-Wpragma-clang-attribute"
#endif
#pragma clang diagnostic ignored "-Wunknown-pragmas"
#pragma clang diagnostic ignored "-Wnullability"
#if __has_attribute(external_source_symbol)
# pragma push_macro("any")
# undef any
# pragma clang attribute push(__attribute__((external_source_symbol(language="Swift", defined_in="ExampleClass",generated_declaration))), apply_to=any(function,enum,objc_interface,objc_category,objc_protocol))
# pragma pop_macro("any")
#endif
SWIFT_CLASS("_TtC12ExampleClass12ExampleClass")
@interface ExampleClass : NSObject
- (void)increment;
- (void)incrementBy:(NSInteger)amount;
- (void)reset;
- (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
@end
#if __has_attribute(external_source_symbol)
# pragma clang attribute pop
#endif
#pragma clang diagnostic pop
#endif
This finding makes it possible to call Swift 5.3 code from Objective-C. By writing a separate code that calls Objective-C from C, you can call Swift from C. In other words, you can freely call Swift and Apple APIs from Elixir. Banzai!
This research result was supported by A-STEP Tryout JPMJTM20H1 which is a support program for optimal development of research results in the research results development project of the Japan Science and Technology Agency.
Recommended Posts