Using Chilkat from Swift on iOS

How Swift uses an Objective-C library

Swift can call Objective-C code directly, but it needs to be told which Objective-C headers to expose. That is the job of the Objective-C bridging header — a single .h file in which you #import the Objective-C headers you want to use. Once the bridging header is configured:

• The imported classes (Chilkat's Cko classes) become available throughout your Swift code — no import statement is needed in your .swift files.
• Objective-C classes, methods, and properties are exposed to Swift — though Swift adapts the names to its own conventions (see How Objective-C names map to Swift), and Foundation types bridge automatically (for example NSString ↔ String).

This is exactly how you would consume any Objective-C library from Swift; Chilkat is no different.

Step 1 — Add an Objective-C bridging header

1. Create the bridging header

   Add a header file to your project named YourProject-Bridging-Header.h and import the Chilkat Cko classes your app uses:

   #import <Foundation/NSObject.h>
   
   #import "chilkat-ios/include/CkoGlobal.h"
   #import "chilkat-ios/include/CkoJsonObject.h"
   #import "chilkat-ios/include/CkoHttp.h"
   // Import each Cko*.h header your app uses.
   // The path depends on where you extracted the Chilkat headers,
   // and must be on your Header Search Paths.

   If you added Chilkat as an XCFramework, the headers travel with it, so you can usually import as #import "CkoJsonObject.h" without a separate path.

2. Point Xcode at the bridging header

   Set Build Settings → Swift Compiler - General → Objective-C Bridging Header to the path of that file (relative to your project). Xcode also offers to create and wire up a bridging header automatically the first time you add an Objective-C file to a Swift project.

Step 2 — Link the library and add linker flags

Add the Chilkat static library (or XCFramework) to your target under Build Phases → Link Binary With Libraries (click +, then Add Other…). The library to link depends on your platform:

• libchilkatIos.a — iOS
• libChilkatCocoa.a — macOS
• libChilkatWatchOS.a — watchOS
• libChilkatTvOS.a — tvOS

Then, in Build Settings → Other Linker Flags, add:

-lresolv -lpthread -lc++

How Objective-C names map to Swift

When Swift imports an Objective-C class, it does not use the Objective-C names verbatim. The Swift compiler adapts them to Swift's naming conventions, which affects three things:

• Method names — the first letter is lower-cased. Objective-C UpdateString becomes Swift updateString.
• Property names — likewise lower-cased. Objective-C EmitCompact becomes Swift emitCompact, and Version becomes version.
• The first argument of a method — in Objective-C the first parameter has no call-site label, but Swift gives it one (the parameter's name). Later arguments keep their existing labels.

For example, the same JSON call in each language:

[json UpdateString: @"test.abc[0].xyz" value: @"Chicago Cubs"];

json.updateString(jsonPath: "test.abc[0].xyz", value: "Chicago Cubs")

Note the three differences: UpdateString → updateString, the first argument gained the label jsonPath:, and the trailing value: label is unchanged.

Calling Chilkat from Swift

A few more things to keep in mind when calling Chilkat from Swift:

• Construction: [[CkoJsonObject alloc] init] becomes CkoJsonObject()! — the initializer returns an implicitly-unwrapped optional, hence the !.
• Strings bridge automatically: a Chilkat method returning NSString * returns a Swift String.
• Numeric properties typed as NSNumber must be set and read as NSNumber in Swift (see the troubleshooting note below).

// No 'import Chilkat' is needed — the bridging header exposes the classes.

let json = CkoJsonObject()!
json.emitCompact = false
json.updateString(jsonPath: "author.name", value: "Chilkat")
print(json.emit()!)

Unlocking Chilkat

Chilkat runs as a fully functional 30-day trial out of the box. Unlock it once at app startup. Pass any non-empty string for the trial, or your license code after purchase:

let glob = CkoGlobal()!
let success = glob.unlockBundle(bundleUnlockCode: "Anything for 30-day trial")
if !success {
    print(glob.lastErrorText!)
}

Common problems