Adding ObjectiveC/Swift Code

For the Objective-C/Swift symbols to be accessible by the Nativescript runtimes the following criteria should be met:

They need to be compiled and linked
Metadata need to be generated for them

The first task is done by the NativeScript CLI by adding the source files to the generated .xcodeproj. For the second one, the Metadata Generator needs to find a module.modulemap of the compiled modules.

For .swift files module.modulemap is not required.

In order to satisfy the above constraints, the developer has to:

1) Place the source files in App_Resources/iOS/src/

2) Create a modulemap for the Objective-C files

Note Swift classes need to be accessible from the Objective-C runtime in order to be used from NativeScript. This can be done by using the @objc attribute or by inheriting NSObject.

For a detailed walkthrough on how to use a native iOS source code in NativeScript here.

Objective C Example

A minimal example for adding native Objective C source code to your NativeScript application:

Create ExampleCrypto.m file with the following content:

// import required header files
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonHMAC.h>
#import "ExampleCrypto.h"

@implementation ExampleCrypto

+ (NSString *)generateHMACWithApiKey:(NSString *) apiKey andApiSecret:(NSString *) apiSecret {
    NSString *hmacData = [NSString stringWithFormat:@"%@%@%@%@%@",apiKey];

    // Make sure the HMAC hash is in hex
    unsigned char outputHMAC[CC_SHA256_DIGEST_LENGTH];
    const char* keyChar = [apiSecret cStringUsingEncoding:NSUTF8StringEncoding];
    const char* dataChar = [hmacData cStringUsingEncoding:NSUTF8StringEncoding];
    CCHmac(kCCHmacAlgSHA256, keyChar, strlen(keyChar), dataChar, strlen(dataChar), outputHMAC);
    NSData* hmacHash = [[NSData alloc] initWithBytes:outputHMAC length:sizeof(outputHMAC)];

    NSString* hmacHashHexString = [[hmacHash description] stringByReplacingOccurrencesOfString:@" " withString:@""];

    // Authorization : base64 of hmac hash -->
    NSString* authorization = [[hmacHashHexString dataUsingEncoding:NSUTF8StringEncoding] base64EncodedStringWithOptions:0];

    return authorization;
}

@end

Create ExampleCrypto.h file with the following content:

#import <Foundation/Foundation.h>

@interface ExampleCrypto : NSObject

+ (NSString *)generateHMACWithApiKey:(NSString *)apiKey andApiSecret:(NSString *)apiSecret;

@end

Create the module.modulemap file with the following content:

module ExampleCrypto {
  header "ExampleCrypto.h"
  export *
}

Call the static method from the ObjectiveC source code just added somewhere in your application.

function generateNativeIOSHMAC() {
  // This if check ensures the following code is only executed on iOS.
  if (global.isIOS) {
    const apiKey = '9292skksd88172alekdd782939ssa'
    const apiSecret = 'f82828282828f992f'

    const base64encryptedKey = ExampleCrypto.generateHMACWithApiKeyandApiSecret(
      apiKey,
      apiSecret
    )
    console.log('base64encryptedKey', base64encryptedKey)
  }
}

Build your NativeScript application by running the following, and you should see the base64encryptedKey print in your terminal.
```
ns clean
ns run ios --no-hmr
```