Swift Language Working with C and Objective-C Specify a bridging header to swiftc


The -import-objc-header flag specifies a header for swiftc to import:

// defs.h
struct Color {
    int red, green, blue;

#define MAX_VALUE 255
// demo.swift
extension Color: CustomStringConvertible {  // extension on a C struct
    public var description: String {
        return "Color(red: \(red), green: \(green), blue: \(blue))"
print("MAX_VALUE is: \(MAX_VALUE)")  // C macro becomes a constant
let color = Color(red: 0xCA, green: 0xCA, blue: 0xD0)  // C struct initializer
print("The color is \(color)")
$ swiftc demo.swift -import-objc-header defs.h && ./demo
MAX_VALUE is: 255
The color is Color(red: 202, green: 202, blue: 208)