Compiling Swift and Objective-C from the Command-Line

example.swift

% ls -l
total 40
-rw-r--r--@ 1 bhamiltoncx  staff  111 Sep 26 14:42 ObjcGreeter.h
-rw-r--r--@ 1 bhamiltoncx  staff  155 Sep 26 14:50 ObjcGreeter.m
-rw-r--r--  1 bhamiltoncx  staff  300 Sep 26 15:06 greetings.swift
-rw-r--r--  1 bhamiltoncx  staff  304 Sep 26 15:06 input.swift
-rw-r--r--  1 bhamiltoncx  staff  165 Sep 26 15:06 main.swift
 
% cat greetings.swift
import Foundation
 
public func sayHello(name: String) {
     print("Hello " + name)
}
 
@objc public class Greeter : NSObject {
    public class func sayHello(name: String) {
        // To access the global function, you have to prefix it with the module name
        greetings.sayHello(name)
    }
}
 
% cat input.swift
import Foundation
 
public func getInput() -> String? {
  let stdin = NSFileHandle.fileHandleWithStandardInput()
  let data = stdin.availableData
  let str = NSString(data: data, encoding: NSUTF8StringEncoding)
  let trimmedStr = str?.stringByTrimmingCharactersInSet(
      NSCharacterSet.whitespaceAndNewlineCharacterSet())
  return trimmedStr as String?
}
 
% cat ObjcGreeter.h
#import <Foundation/Foundation.h>
 
@interface ObjcGreeter : NSObject
 
+ (void)sayHello:(NSString *)name;
 
@end
 
% cat ObjcGreeter.m
#import "ObjcGreeter.h"
// Generated by the Swift compiler
#import "greetings-Swift.h"
 
@implementation ObjcGreeter
 
+ (void)sayHello:(NSString *)name {
    [Greeter sayHello:name];
}
 
@end
 
% cat main.swift
import greetings
 
print("What is your name?")
let name = getInput() ?? "(unable to decode input)"
sayHello(name)
 
ObjcGreeter.sayHello("to Swift from Objective-C")
 
 
% swift -frontend -c -module-name greetings -sdk `xcrun --sdk macosx --show-sdk-path` -target x86_64-apple-macosx10.11 -emit-module -emit-module-path greetings.swiftmodule -enable-objc-interop -emit-objc-header -emit-objc-header-path greetings-Swift.h -c -o libgreetings.o greetings.swift input.swift
 
% clang -isysroot `xcrun --sdk macosx --show-sdk-path` -mmacosx-version-min=10.11 -c -I . ObjcGreeter.m
 
% swift -frontend -c -I . -c -primary-file main.swift -sdk `xcrun --sdk macosx --show-sdk-path` -target x86_64-apple-macosx10.11 -enable-objc-interop -import-objc-header ObjcGreeter.h main.swift    
                                                                                                     
% clang -isysroot `xcrun --sdk macosx --show-sdk-path` -mmacosx-version-min=10.11 -L/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift_static/macosx -Xlinker -force_load_swift_libs -lswiftRuntime -lc++ -framework Foundation -Xlinker -add_ast_path -Xlinker greetings.swiftmodule -o hello main.o libgreetings.o ObjcGreeter.o
 
% ./hello
What is your name?
Ben
Hello Ben
Hello to Swift from Objective-C
 
% printf "\xAB\xCD\xEF" | ./hello
What is your name?
Hello (unable to decode input)
Hello to Swift from Objective-C
 
% echo 💩 | ./hello              
What is your name?
Hello 💩
Hello to Swift from Objective-C