How to Seamlessly Mix Swift and Objective‑C in a Single iOS Project

Mixing Swift and Objective‑C in the Same Project

In Swift iOS development you often need to combine Swift and Objective‑C code. This article explains the two directions—Swift calling Objective‑C and Objective‑C calling Swift—along with the required Xcode configuration and code examples.

Swift accesses Objective‑C

Use a bridging header (ProductName-Bridging-Header.h) to import the Objective‑C class you want to expose, then instantiate and use that class directly in Swift.

Example steps: create an empty project, add a Swift class, let Xcode generate the bridging header, import the Objective‑C header, and write Swift code such as:

import UIKit

class SwiftClass01: NSObject {
    var con: ViewController?

    override init() {
        super.init()
        self.con = ViewController()
    }
}

Objective‑C accesses Swift

In Build Settings search for “Swift Compiler” and ensure the generated header (ProductName-Swift.h) is available. Import this header in the Objective‑C file and call Swift methods that are marked @objc and public.

Key points:

Methods that Objective‑C should call must be annotated with @objc.

Only public methods appear in the generated header.

The generated header automatically registers all Swift classes with an @interface.

Mixing a Swift Framework with an Objective‑C Host App

Create a Swift framework project (e.g., QiSwiftSdk.xcodeproj) and add it to the host app. In the host’s Build Phases set the framework as a target dependency.

In the host’s Objective‑C code, import the framework’s generated Swift header and call Swift classes that are declared open and whose methods are @objc public.

Important notes:

Expose Swift classes with the open keyword.

Mark callable methods with @objc public.

The framework’s own header (QiSwiftSdk.h) does not need additional modifications.

The framework can also contain its own bridging header for internal mixing.